Effectiveness of COVID-19 Vaccines against SARS-CoV-2 Infection in a Healthcare Worker Cohort: A Prospective Study

Effectiveness of COVID-19 Vaccines against SARS-CoV-2 Infection in a Healthcare Worker Cohort: A Prospective Study | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Effectiveness of COVID-19 Vaccines against SARS-CoV-2 Infection in a Healthcare Worker Cohort: A Prospective Study Sepideh Mahdavi, Mostafa Enayatrad, Shahrbanoo Goli, Fariba Zare This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7289111/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 15 You are reading this latest preprint version Abstract Introduction: A vaccine's ability to protect against disease acquisition is considered one of its most important aspects of effectiveness. The present study aimed to determine the effectiveness of COVID-19 vaccines among healthcare workers (HCWs). Materials and Methods This was a prospective cohort study conducted with HCWs from April 2021 to May 2022. We investigated the effectiveness of the AZD1222, Sinopharm, and Sputnik V vaccines against SARS-CoV-2 infection (diagnosed by PCR testing). For this purpose, vaccination data from 3365 HCWs were collected, and vaccine effectiveness was estimated via multivariable Cox models and the incidence rate of SARS-CoV-2 infection per 100,000 person-time. Result Among the 3365 participants, all individuals received at least one dose, 95.3% received at least two doses, and 36.7% of those who received two doses also received three doses of the COVID-19 vaccine. The overall vaccine effectiveness after three doses was estimated to be 92% (95% confidence interval: 81–97). The effectiveness of the AZD1222, Sinopharm, and Sputnik V vaccines after three doses was estimated to be 98% (95% confidence interval: 96–97), 93% (95% confidence interval: 42–99), and 83% (95% confidence interval: 13–97), respectively. Conclusion The results of this study indicate that completing vaccination and receiving second and third doses significantly increased vaccine effectiveness and was highly effective in preventing SARS-CoV-2 infection in HCWs. Furthermore, among the vaccines investigated, vaccination with three doses of the AZD1222 vaccine showed the highest effectiveness. COVID-19 vaccines Healthcare workers Effectiveness Introduction The COVID-19 pandemic represents one of the most significant global health crises of the 21st century, affecting billions of people worldwide and causing profound disruptions to daily life while imposing substantial financial burdens on healthcare systems ( 1 , 2 ). Non-pharmaceutical interventions (NPIs), including social distancing, mask mandates, and contact tracing, were initially deployed as primary control strategies and effectively reduced transmission rates ( 3 , 4 ). The rapid development and global deployment of vaccines subsequently marked a critical turning point in pandemic control, significantly reducing severe disease, hospitalizations, and mortality ( 5 , 6 ). Vaccination remains one of the most effective and cost-efficient public health interventions for preventing and controlling infectious diseases, particularly during pandemics ( 7 , 8 ). The rapid development and deployment of safe and efficacious COVID-19 vaccines represented a pivotal milestone toward ending the pandemic ( 9 ). However, despite widespread vaccine distribution, ongoing evaluation of vaccine effectiveness is crucial to understanding both the benefits and potential adverse effects of vaccination programs. Multiple studies have demonstrated that vaccine effectiveness against SARS-CoV-2 infection wanes over time, with a pronounced decline observed against emerging variants such as Omicron ( 10 – 12 ). In Iran, the National COVID-19 Headquarters prioritized high-risk groups, such as healthcare workers, elderly individuals, and individuals with underlying conditions for receiving the vaccine. This prioritization was implemented in most countries around the world to provide vaccines to people at risk ( 13 – 15 ). In this context, various vaccines, such as AZD1222 (AstraZeneca), Sinopharm, and Sputnik V, have been used in Iran. The effectiveness of these vaccines has been reported in different global studies depending on the type of platform, storage conditions, and type of circulating strains; for example, the effectiveness of AstraZeneca in the UK was reported to be approximately 70%, and inactivated Chinese vaccines varied from 50–90% ( 16 , 17 ). Recent studies have shown that even during Omicron waves, receiving a booster dose increases vaccine effectiveness among healthcare workers ( 18 – 20 ). Additionally, CDC reports from the United States indicated that mRNA vaccines were up to 90% effective in preventing infection, both symptomatic and asymptomatic ( 21 , 22 ). Healthcare workers (HCWs) face an elevated risk of contracting viral infections due to their direct and frequent contact with patients and clinical environments. Moreover, they may serve as vectors, transmitting the virus to other vulnerable populations within the community ( 23 – 25 ). According to the World Health Organization (WHO), the HCW group includes physicians, nurses, laboratory technicians, support staff, and healthcare facility administrators ( 26 ). A systematic review estimated that approximately 3.9% of global COVID-19 cases occurred among HCWs. In contrast, a study conducted in Iran reported a substantially higher proportion, with 5.62% of infections observed in this group ( 27 , 28 ). Therefore, effective vaccination of this group not only supports their personal health but also contributes to reducing the transmission of the disease within the broader community. However, differences in vaccine acceptance, health literacy, access to healthcare services, and even cultural beliefs across regions may influence the effectiveness of vaccination efforts. Despite numerous international studies ( 21 , 29 ), there is still insufficient evidence regarding the effectiveness of COVID-19 vaccines among Iranian healthcare workers, particularly at the regional level. Therefore, the present study aimed to evaluate the effectiveness of different COVID-19 vaccines in preventing SARS-CoV-2 infection among healthcare workers at Shahroud University of Medical Sciences. Materials and methods Data collection and vaccination protocol This study is a cohort study conducted among HCWs at Shahroud University of Medical Sciences in northeastern Iran. In this investigation, HCWs employed in various departments of hospitals, health centers, and administrative sections of Shahroud University of Medical Sciences were enrolled. Eligibility criteria included having received at least one dose of any of the following vaccines: AZD1222, Sinopharm (BBIBP-CorV), and Sputnik V, with their vaccination data registered in the Comprehensive COVID-19 Information Center. According to the protocol established by the Center for Disease Management (CEM) in Iran ( 30 ), the Comprehensive COVID-19 Information Database was initiated in March 2020, coinciding with the onset of the COVID-19 pandemic. This database systematically records comprehensive information for all diagnosed individuals, including HCWs. The recorded data included RT‒PCR test results, CT scan findings, demographic information, treatment progression, and disease outcomes. Furthermore, with the commencement of HCW vaccination in April 2021, relevant vaccination data were also integrated into this database. For each HCW who was willing to be vaccinated, and on the basis of the Ministry of Health guidelines and vaccine availability, one of the three vaccines, AZD1222, Sinopharm (BBIBP-CorV), or Sputnik V, was administered. Exposures and Outcomes To evaluate vaccine effectiveness, exposure period was considered a time-dependent variable. Individual exposure was categorized on the basis of vaccine status and type: unvaccinated (no exposure), one-dose vaccinated, two-dose vaccinated, and three-dose vaccinated. Given that vaccination has occurred over time, individuals have transitioned between groups, and their membership in each group has changed accordingly. Consequently, by the end of the study, with all individuals having received at least one vaccine dose, no participant remained in the unvaccinated group. The study groups were defined as follows: The partial immunity group: included individuals who had received at least one dose of any vaccine type and were followed from 14 days after the first dose until 14 days after the second dose. The full immunity group: included individuals who had received two doses of any vaccine type and were followed from 14 days after the second dose until 14 days after the third dose. The Booster Immunity group: This group consisted of individuals who had received three doses of any vaccine type and were followed from 14 days after the third dose until the end of the study. The primary outcome investigated in this study was confirmed COVID-19 infection (diagnosed via RT‒PCR). For this purpose, data on disease incidence among healthcare workers were retrieved from the Comprehensive COVID-19 Management System. The primary criterion for determining disease acquisition in this design was a positive RT‒PCR diagnostic test. Statistical analysis The incidence rate was calculated per 100,000 person-time, along with its 95% confidence interval (95% CI), across specific time intervals. These intervals included periods from 14 days post-receipt of one vaccine dose until 14 days post-receipt of the next dose. For the third dose, this calculation extended from 14 days after the third dose was received until the study's end (May 20, 2022). Vaccination status was defined as a categorical variable. To estimate the adjusted hazard ratios (HRs) for COVID-19 infection, we employed an extended Cox regression model. In this model, vaccine status was treated as a time-dependent variable, and calendar time served as the timescale. Finally, within the Cox models, adjusted hazard ratios (HRs) with their 95% CIs were reported for sex, age, workplace, type of work activity, and vaccine dose received. Results Between April 4, 2021, and May 20, 2022, a total of 3365 individuals participated in the present study. All participants had received at least one dose of the vaccine under investigation. Of these, 95.3% had received at least two doses, and 36.7% of those who had received two doses also received a third dose of one of the available COVID-19 vaccines. Table 1 shows the distribution of participants by vaccination status, vaccine brand, demographic characteristics such as age and sex, and sector of activity. Table 1: Characteristics of Study Participants by Vaccination Dose Received Variable One Dose Received Two Dose Received Three Dose Received Enrollment start date 04 April 2021 09 March 2021 19 September 2021 Participants, n (%) 3365 (100.0) 3207 (95.3) 1177 (36.7) Age (years), Mean (SD) 34.71 (11.2) 34.97 (11.2) 37.60 (11.7) Sex, n (%) Males 1355 (40.3) 1297 (40.4) 489 (41.5) Females 2010 (59.7) 1910 (59.6) 688 (58.5) Staff Group, n (%) Hospital a 1413 (42.0) 1340 (41.8) 515 (43.8) Health services 398 (11.8) 369 (11.5) 139 (11.8) Administrative b 1554 (46.2) 1498 (46.7) 523 (44.4) Workplace, n (%) Hospital staff 1925 (57.2) 1874 (58.4) 744 (63.2) Health centers 240 (7.1) 219 (6.8) 85 (7.2) Administrative centers 1200 (35.7) 1114 (34.7) 348 (29.6) Vaccine , n (%) AZD1222 1654 (49.2) 1555 (48.5) 960 (81.6) Sinopharm 578 (17.2) 534 (16.7) 120 (10.2) Sputnik V 1133 (33.7) 1118 (34.9) - Other - - 97 (8.2) Hospital staff: Includes doctors, nurses, and other medical personnel directly working in hospitals. administrative: Refers to nonclinical or management staff within the healthcare system. The incidence rate of COVID-19 among vaccinated individuals was 42.65 (95% CI: 39.12 to 46.49) per 100,000 person-days. Based on vaccine brand, the incidence rate in recipients of the AstraZeneca vaccine was 40.55 (95% CI: 36.38-45.20), that of the Sinopharm vaccine was 33.58 (95% CI: 26.43-42.66), and that of the Sputnik V vaccine was 55.57 (95% CI: 48.86-63.21) per 100,000 person-days. Regardless of vaccine brand, the incidence rate was significantly higher in females, individuals aged 18-49 years, health services staff, and those working in health centers. Table 2 reports these rates stratified by vaccine brand, sex, age group, workplace, and the incidence rate of COVID-19 among individuals who had received a third vaccine dose was higher than that among those who had received one or two doses of any vaccine brand, regardless of the specific brand. Furthermore, for each received dose, the incidence rate was consistently higher in females than in males, higher in health service staff than in other occupational groups, and higher in those working in health centers than in other workplaces. However, the incidence rate in the 18-49 years age group after receiving the first dose was lower than that in the over 50 years age group, whereas it was higher in the 18-49 years age group after receiving the second and third doses. The incidence of COVID-19 was significantly higher after the first dose of the AZ1222 vaccine (30.50% CI: 23.42-39.73), after the second dose of the Sputnik V vaccine (54.29% CI: 46.41-63.52), and after the third dose of the AZ1222 vaccine (72.27% CI: 59.80-89.79). Table 3 shows the incidence rates in vaccine recipients based on each dose received and the variables of sex, age, place of work, and type of work. Table 2 . Incidence Rate of COVID-19 Cases per 100,000 Person-Days (95% CI) Variable Number of Events (n) Incidence Rate (95% CI) a Vaccine Brand Overall Vaccine 517 42.65 (39.12-46.49) AZ1222 326 40.55 (36.38-45.20) Sinopharm 67 33.58 (26.43-42.66) Sputnik V 232 55.57 (48.86-63.21) Sex Males 187 38.00 (32.93-43.86) Females 330 45.82 (41.13-51.04) Age Group 18-49 years 460 43.42 (39.63-47.57) ≥ 50 years 57 39.42 (30.41-51.11) Staff Group Hospital staff b 341 48.83 (43.91-54.30) Health services 50 58.64 (44.44-77.37) Administrative centers c 126 29.39 (24.68-35.00) Workplace Hospital 278 54.95 (48.85-61.80) Health centers 81 56.78 (45.66-70.59) Administrative centers 158 28.03 (23.98-32.76) Incidence, cases per 100 000 person-days (95% CI) Hospital staff: Includes doctors, nurses, and other medical personnel directly working in hospitals. administrative: Refers to nonclinical or management staff within the healthcare system Table 3. Incidence Rate of COVID-19 Infection by Vaccination Dose and Subgroup Characteristics Variable One Dose Received Two Dose Received Three Dose Received Event (n) Incidence Rate (95% CI) a Event (n) Incidence Rate (95% CI) a Event (n) Incidence Rate (95% CI) a Any Vaccine Males 28 27.13 (18.73-39.29) 122 38.04 (31.86-45.43) 36 55.65 (40.14-77.15) Females 45 28.61 (21.36-38.33) 216 45.87 (40.15-52.42) 69 78.52 (62.02-99.42) 18-49 years 62 26.46 (20.63-33.94) 309 44.39 (39.70-49.62) 88 72.02 (58.44-88.76) ≥ 50 years 11 44.81 (24.82-80.93) 29 32.19 (22.37-46.32) 17 58.46 (36.34-94.04) Hospital staff b 45 33.19 (24.78-44.45) 221 48.28 (42.32-55.09) 75 75.32 (60.07-94.45) Health services staff 11 49.96 (27.67-90.22) 30 57.28 (40.05-81.92) 8 76.98 (38.49-153.93) Administrative staff c 17 16.52 (10.27-26.58) 87 30.91 (25.05-38.144) 22 51.64 (34.00-78.44) Working in hospital 28 27.41 (18.93-39.71) 183 55.40 (47.93-64.04) 67 96.70 (76.11-122.86) Working in Health centers 18 54.66 (34.43-86.75) 48 52.46 (39.53-69.61) 14 80.03 (47.40-135.13) Working in Administrative centers 27 21.53 (14.76-31.39) 107 28.94 (23.94-34.98) 24 36.48 (24.45-54.43) After receiving the dose 73 28.02 (22.28-35.25) 338 42.70 (38.38-47.51) 105 68.82 (56.84-83.33) AZ1222 Vaccine Males 20 27.55 (17.77-42.71) 46 30.97 (23.20-41.35) 33 60.37 (42.92-84.92) Females 35 32.49 (23.32-45.25) 90 41.36 (33.64-50.86) 60 83.03 (64.47-106.94) 18-49 years 45 27.65 (20.64-37.03) 124 37.91 (31.79-45.20) 79 79.25 (63.56-98.80) ≥ 50 years 10 59.40 (31.96-110.41) 12 31.47 (17.87-55.41) 14 53.97 (31.96-91.13) Hospital staff b 32 34.12 (24.13-48.26) 84 39.51 (31.90-48.93) 67 76.25 (60.01-96.88) Health services staff 9 54.51 (28.36-104.77) 14 53.59 (31.74-90.50) 8 83.22 (41.61-166.40) Another staff c 14 19.99 (11.83-33.75) 38 29.83 (21.71-41.00) 18 61.14 (38.52-97.04) Working in hospital 17 27.80 (17.28-44.72) 52 45.61 (34.75-59.86) 62 105.64 (82.36-135.50) Working in Health centers 15 62.25 (37.52-103.25) 22 59.17 (38.96-89.86) 14 85.89 (50.87-145.03) Working in Administrative centers 23 24.19 (16.07-36.40) 62 28.85 (22.49-37.01) 17 32.73 (20.35-52.66) After receiving the dose 55 30.50 (23.42-39.73) 136 37.15 (31.40-43.95) 93 72.27 (59.80-89.79) Sinopharm Vaccine Males 4 34.12 (12.80-90.91) 17 33.88 (21.06-54.50) 2 33.72 (8.43-134.85) Females 5 20.64 (8.59-49.60) 29 32.98 (22.92-47.46) 6 60.00 (26.95-133.56) 18-49 years 9 25.71 (13.38-49.42) 43 32.78 (24.31-44.21) 7 49.37 (23.54-103.57) ≥ 50 years 0 0 3 45.16 (14.56-140.04) 1 57.04 (8.03-404.96) Hospital staff b 7 77.00 (36.71-161.53) 17 53.54 (33.28-86.13) 4 85.17 (31.96-226.95) Health services staff 0 0 2 86.28 (21.57-94.88) 0 0 Another staff c 2 8.02 (2.00-32.08) 27 25.95 (17.79-37.84) 4 37.62 (14.12-100.25) Working in hospital 5 34.82 (14.49-83.67) 20 38.99 (25.16-60.44) 3 46.38 (14.96-143.83) Working in Health centers 1 73.85 (10.40-85.30) 2 65.92 (16.48-69.57) 0 0 Working in Administrative centers 3 22.82 (15.29-34.04) 24 28.64 (19.19-42.73) 5 56.74 (23.61-136.32) After receiving the dose 9 25.04 (13.03-48.12) 46 33.30 (24.94-44.46) 8 50.22 (25.11-100.42) Sputnik V Vaccine Males 4 21.15 (7.93-56.36) 59 48.37 (37.47-62.43) - - Females 5 19.76 (8.22-47.49) 97 58.67 (48.08-71.58) - - 18-49 years 8 21.88 (10.94-43.75) 142 59.70 (50.64-70.37) - - ≥ 50 years 1 14.71 (2.07-49.10) 14 30.90 (18.30-52.17) - - Hospital staff b 6 18.33 (8.23-40.82) 120 56.24 (47.03-67.26) - - Health services staff 2 55.89 (13.97-103.50) 14 58.48 (34.64-98.75) - - Another staff c 1 12.65 (1.78-89.80) 22 43.98 (28.95-66.79) - - Working in hospital 6 22.54 (10.12-50.17) 111 67.26 (55.85-81.02) - - Working in Health centers 2 26.73 (6.68-106.89) 24 46.79 (31.36-69.82) - - Working in Administrative centers 1 9.90 (1.39-70.28) 21 29.57 (19.28-45.35) - - After receiving the dose 9 20.36 (10.59-39.13) 156 54.29 (46.41-63.52) - - Incidence, cases per 100 000 person-days (95% CI) Hospital staff: Includes doctors, nurses, and other medical personnel directly working in hospitals. administrative: Refers to nonclinical or management staff within the healthcare system Cox regression analysis revealed that the risk of disease was higher in females than in males, with an HR of 1.28 (95% CI: 1.07-1.54) for females compared with males. Furthermore, a significantly higher hazard ratio was observed in females who had received the AZD1222 vaccine. For every one-year increase in age, the hazard ratio increased. Compared with staff working in hospitals, staff working in health services and administrative sectors had hazard ratios of 0.96 (95% CI: 0.74-1.25) and 0.50 (95% CI: 0.74-1.22), respectively, indicating a lower risk of infection. Across all three periods of partial, full, and booster (or primary, secondary, and tertiary immunity phases of the vaccine), the AZD1222 vaccine demonstrated significantly better efficacy than the other vaccines did. Additionally, receiving three doses of any vaccine conferred increased immunity in individuals (Table 4). Table 4. Hazard Ratios a for COVID-19 Infection by Vaccine Brand and Participant Characteristics Variable AZD1222 Sinopharm Sputnik V any vaccine Received Sex: Female vs. Male 1.48 (1.11 – 1.97) 1.12 (0.65 – 1.90) 1.14 (0.88 – 1.49) 1.28 (1.07 – 1.54) Age (per years increase) 1.01 (0.99 – 1.02) 1.02 (1.00 – 1.05) 0.99 (0.98 – 1.00) 1.01 (1.00 – 1.02) 0–13 days after first dose Ref Ref Ref Ref Partial immunity b 0.20 (0.09 – 0.42) 0.63 (0.08 – 4.75) 0.56 (0.11 – 2.89) 0.45 (0.20 – 1.00) Full immunity c 0.11 (0.05 – 0.22) 0.45 (0.06 – 3.18) 0.64 (0.13 – 3.20) 0.36 (0.16 -0.79) Booster immunity d 0.02 (0.01 -0.04) 0.07 (0.01 – 0.58) 0.17 (0.03 – 0.87) 0.08 (0.03 – 0.19) Working in hospital Ref Ref Ref Ref Working in Health centers 1.91 (1.19 – 3.05) 1.13 (0.34 – 3.73) 0.56 (0.39 – 0.82) 0.96 (0.74 – 1.25) Working in Administrative centers 1.05 (0.69 – 1.60) 0.79 (0.44 – 1.41) 0.42 (0.31 – 0.56) 0.50 (0.74 – 1.22) Hazard Ratio in extended Cox regression model, with vaccine status as time- dependent variable and calendar time as the timescale by confidence interval 95% Defined as the period between the 14th day after the first dose and 14 days after the second dose. Defined as the period between the 14th day after the second dose and 14 days after the three doses. Defined as the period between the 14th day after the three dose and the end of follow-up. Discussion The present cohort study estimated that the overall effectiveness of COVID-19 vaccines among HCWs was 92% after receiving three vaccine doses. The effectiveness of the AZD1222, Sinopharm, and Sputnik V vaccines after three doses was estimated to be 98%, 93%, and 83%, respectively. These findings align with the results of effectiveness studies conducted on HCWs in England, Israel, and Chile, all of which reported favorable efficacy for COVID-19 vaccines ( 31 – 33 ). Given the differences in vaccination strategies worldwide, it is important to evaluate the effectiveness of each vaccination program under different scenarios. Although the results obtained indicate sufficient protection from vaccines against COVID-19 infection, considering HCWs' high exposure risk to the virus, the gradual decline in immunity over time, and the emergence of new viral variants, this level of immunity could be further diminished. However, receiving three doses of each of the vaccines in the vaccination program may have been able to provide significant immunity against COVID-19 infection. In the present study, the incidence rate of COVID-19 significantly increased during the follow-up periods after the third and second doses compared with the first dose. This finding is consistent with results from a study on the AZD1222 vaccine in Scotland and Brazil ( 34 ), which also reported an increased incidence after the second dose. This increase in incidence could be attributed to several factors, including a decrease in vaccine effectiveness over time, an extended interval between doses, or shifts in viral variants. Furthermore, population-based studies in England and Wales indicated a decrease in antibody levels following the second dose of AZD1222. However, these studies still reported higher effectiveness in preventing disease acquisition ( 35 , 36 ). Importantly, in our study, individuals received their vaccinations at different times. Consequently, the occurrence of COVID-19 could be influenced by the timing of individuals' entry into the study and their duration of follow-up. Moreover, the emergence of newer viral variants over time (such as the delta and subsequently Omicron variants, which predominated during the study period) might lead to a reduction in vaccine effectiveness. Another crucial consideration is that the age and sex distributions of individuals vary by vaccine brand. Since the risk of infection differs on the basis of age and sex, a straightforward comparison of incidence rates solely on the basis of vaccine brand is not feasible. Therefore, to control for these confounding variables, Cox regression analysis was employed. In the present study, differences in the risk of disease after vaccination were observed across occupational groups. These differences suggest that other factors influencing the risk of infection among HCWs receiving a vaccination. These factors include time since vaccination, age, sex, dominant virus strain, severity of the epidemic, underlying diseases, and level of community attention to prevention programs. This finding is consistent with a vaccination study of HCWs in England ( 37 ). In the present study, the effectiveness of the AZD1222 vaccine was significantly higher than that of the other two vaccines in all three periods of partial, full and booster immunity. Notably, the effectiveness of the Sinopharm vaccine during the booster immunization period was somewhat comparable to that of the AZD1222 vaccine during the same period. Similar findings, particularly concerning the partial immunity period, have also been reported in a large multicenter study conducted in the Islamic Republic of Iran ( 38 ). The AZD1222 vaccine showed 89% effectiveness after two doses and 98% effectiveness after three doses. As previously mentioned, vaccine effectiveness is influenced by various factors. Consequently, these factors lead to discrepancies in reported studies. For instance, a study conducted in Scotland ( 39 ) on HCWs reported that the effectiveness of the AstraZeneca vaccine was 30% (95% CI: 22–37%) 14 days after the first dose and 54% (95% CI: 30–70%) 14 days after the second dose. In a study conducted in the UK ( 36 ) on HCWs, the effectiveness of the AstraZeneca vaccine was 56% and 62% at 28–34 and 35–48 days after receiving the vaccine, respectively. Furthermore, another study in France ( 40 ) on HCWs reported 86% and 100% effectiveness 14 days after receiving the first and second doses of the AstraZeneca vaccine, respectively. Moreover, in population-based studies, for example, a phase III clinical trial conducted on three continents revealed that the AstraZeneca vaccine was 70.4% effectiveness after two doses ( 41 ). Observational studies have also reported effectiveness rates ranging from 65–86% after a single dose ( 35 , 42 , 43 ). In the present study, the effectiveness of the Sinopharm vaccine was reported to be 55% after two doses and 93% after three doses. In contrast, studies conducted in Hungary ( 42 ) and Chile ( 31 ) reported effectiveness rates of 86.9% and 87.8%, respectively, after the second dose of this vaccine. The effectiveness of the Sputnik V vaccine was reported to be 44% after one dose and 36% after two doses. Notably, for booster doses among Sputnik V recipients, other vaccine types were utilized (as the third dose of Sputnik V was not available in Iran during the study period). This finding contrasts with the results of a phase III clinical trial, which reported a Sputnik V vaccine effectiveness of 85.7% one week after the second dose ( 44 ), and an observational study in Hungary ( 42 ) which reported 97.1% effectiveness after two doses. The Hungarian study ( 42 ) also reported that the AstraZeneca vaccine effectiveness at over 95%, and the Sinopharm vaccine effectiveness at 66.1%. Furthermore, a study in Abu Dhabi ( 45 ) indicated that the effectiveness of the Sinopharm vaccine was 80% in individuals who had received two doses. These discrepancies in vaccine effectiveness estimates across different studies can be attributed to various factors, including variations in study design; vaccination protocols employed; characteristics of the studied populations (e.g., prevalence, age, and underlying comorbidities); and variations in the duration of postvaccination follow-up and the number of doses administered. This study has several limitations. First, our effectiveness estimates focused solely on infections confirmed by PCR diagnostic tests. Other outcomes, such as hospitalization and mortality, were not evaluated in the final analysis because of their very low incidence within the study cohort during the investigation period. Second, we assessed the effectiveness against any SARS-CoV-2 infection and did not perform viral genome sequencing throughout the study period. This is particularly relevant, as B.1.617.2 (Delta) and subsequently Omicron variants became predominant during the study. Conclusion This study demonstrated that completing vaccination and receiving the second and third doses significantly increased vaccine effectiveness against SARS-CoV-2 infection. This enhanced efficacy played a crucial role in preventing SARS-CoV-2 infection among healthcare workers (HCWs). Among the vaccines investigated, vaccination with three doses of the AZD1222 vaccine showed the highest effectiveness. Declarations Ethics approval and consent to participate This study was approved by the Ethics Committee of Shahroud University of Medical Sciences (approval number: IR.SHMU.REC.1400.076]). Consent for publication Not applicable. Availability of data and materials The datasets used and/or analyzed during the current study are available from the corresponding author upon reasonable request. Competing interests The authors declare that they have no competing interests. Funding This study was funded by Shahroud University of Medical Sciences. The funding body had no role in the design of the study, data collection, analysis, interpretation, or writing of the manuscript. Authors' contributions SM and ME conceptualized the study and contributed to the study design. ME and SHG were responsible for data collection and statistical analysis. FZ and SM wrote the initial draft of the manuscript. ME critically revised the manuscript and supervised the study. ME contributed to the statistical analysis and interpretation of results All authors read and approved the final manuscript. Acknowledgements The authors would like to thank all the staff of Shahroud University of Medical Sciences for their support during the study. References Gebru AA, Birhanu T, Wendimu E, Ayalew AF, Mulat S, Abasimel HZ, et al. Global burden of COVID-19: Situational analyis and review. Hum Antibodies. 2021;29(2):139–48. Levin AT, Owusu-Boaitey N, Pugh S, Fosdick BK, Zwi AB, Malani A, et al. Assessing the burden of COVID-19 in developing countries: systematic review, meta-analysis and public policy implications. BMJ Glob Health. 2022;7(5):e008477. Dhanani LY, Franz B. A meta-analysis of COVID-19 vaccine attitudes and demographic characteristics in the United States. Public Health. 2022;207:31–8. Wagner AL, Sheinfeld Gorin S, Boulton ML, Glover BA, Morenoff JD. Effect of vaccine effectiveness and safety on COVID-19 vaccine acceptance in Detroit, Michigan, July 2020. Hum Vaccin Immunother. 2021;17(9):2940–5. Diani S, Leonardi E, Cavezzi A, Ferrari S, Iacono O, Limoli A, et al. Sars-Cov-2—the role of natural immunity: A narrative review. Journal of clinical medicine. 2022;11(21):6272. Dong Y, Dai T, Wei Y, Zhang L, Zheng M, Zhou F. A systematic review of SARS-CoV-2 vaccine candidates. Signal Transduct Target Ther. 2020;5(1):237. Krammer F. SARS-CoV-2 vaccines in development. Nature. 2020;586(7830):516–27. Rozek LS, Jones P, Menon A, Hicken A, Apsley S, King EJ. Understanding Vaccine Hesitancy in the Context of COVID-19: The Role of Trust and Confidence in a Seventeen-Country Survey. Int J Public Health. 2021;66:636255. van Riel D, de Wit E. Next-generation vaccine platforms for COVID-19. Nat Mater. 2020;19(8):810–2. Awadasseid A, Wu Y, Tanaka Y, Zhang W. Current advances in the development of SARS-CoV-2 vaccines. Int J Biol Sci. 2021;17(1):8–19. Shaw J, Stewart T, Anderson KB, Hanley S, Thomas SJ, Salmon DA, et al. Assessment of US Healthcare Personnel Attitudes Towards Coronavirus Disease 2019 (COVID-19) Vaccination in a Large University Healthcare System. Clin Infect Dis. 2021;73(10):1776–83. Gala D, Parrill A, Patel K, Rafi I, Nader G, Zhao R, et al. Factors impacting COVID-19 vaccination intention among medical students. Human vaccines & immunotherapeutics. 2022;18(1):2025733. Ogilvie GS, Gordon S, Smith LW, Albert A, Racey CS, Booth A, et al. Intention to receive a COVID-19 vaccine: results from a population-based survey in Canada. BMC Public Health. 2021;21(1):1017. Terry E, Cartledge S, Damery S, Greenfield S. Factors associated with COVID-19 vaccine intentions during the COVID-19 pandemic; a systematic review and meta-analysis of cross-sectional studies. BMC Public Health. 2022;22(1):1667. Sherman SM, Sim J, Cutts M, Dasch H, Amlôt R, Rubin GJ, et al. COVID-19 vaccination acceptability in the UK at the start of the vaccination programme: a nationally representative cross-sectional survey (CoVAccS–wave 2). Public health. 2022;202:1–9. Creech CB, Walker SC, Samuels RJ. SARS-CoV-2 Vaccines. JAMA. 2021;325(13):1318–20. Lu J, Wen X, Guo Q, Ji M, Zhang F, Wagner AL, et al. Sensitivity to COVID-19 Vaccine Effectiveness and Safety in Shanghai, China. Vaccines (Basel). 2021;9(5):472. Gaio V, Santos AJ, Amaral P, Viana JF, Antunes I, Pacheco V, et al. COVID-19 vaccine effectiveness among healthcare workers: a hospital-based cohort study. BMJ open. 2023;13(5):e068996. Rubin-Smith JE, Castro MYR, Preza I, Hasibra I, Sulo J, Fico A, et al. Primary series COVID-19 vaccine effectiveness among healthcare workers in Albania, February–December 2021. IJID regions. 2023;8:19–27. Savulescu C, Prats-Uribe A, Brolin K, Lovrić Makarić Z, Uusküla A, Panagiotakopoulos G, et al. Incidence of SARS-CoV-2 infection among European healthcare workers and effectiveness of the first booster COVID-19 vaccine, VEBIS HCW observational cohort study, May 2021–May 2023. Vaccines. 2024;12(11):1295. Fowlkes A. Effectiveness of COVID-19 vaccines in preventing SARS-CoV-2 infection among frontline workers before and during B. 1.617. 2 (Delta) variant predominance—eight US locations, December 2020–August 2021. MMWR Morbidity and Mortality Weekly Report. 2021;70. Ghosh S, Shankar S, Chatterjee K, Chatterjee K, Yadav AK, Pandya K, et al. COVISHIELD (AZD1222) VaccINe effectiveness among healthcare and frontline Workers of INdian Armed Forces: Interim results of VIN-WIN cohort study. medical journal armed forces india. 2021;77:S264-S70. Mutambudzi M, Niedzwiedz C, Macdonald EB, Leyland A, Mair F, Anderson J, et al. Occupation and risk of severe COVID-19: prospective cohort study of 120 075 UK Biobank participants. Occupational and environmental medicine. 2021;78(5):307–14. Rhodes S, Wilkinson J, Pearce N, Mueller W, Cherrie M, Stocking K, et al. Occupational differences in SARS-CoV-2 infection: analysis of the UK ONS COVID-19 infection survey. J Epidemiol Community Health. 2022;76(10):841–6. Benenson S, Oster Y, Cohen MJ, Nir-Paz R. BNT162b2 mRNA Covid-19 vaccine effectiveness among health care workers. New England Journal of Medicine. 2021;384(18):1775–7. World Health Organization. Working together for health: the world health report 2006. 2006. Bandyopadhyay S, Baticulon RE, Kadhum M, Alser M, Ojuka DK, Badereddin Y, et al. Infection and mortality of healthcare workers worldwide from COVID-19: a systematic review. BMJ Glob Health. 2020;5(12). Sabetian G, Moghadami M, Hashemizadeh Fard Haghighi L, Shahriarirad R, Fallahi MJ, Asmarian N, et al. COVID-19 infection among healthcare workers: a cross-sectional study in southwest Iran. Virology journal. 2021;18(1):58. Keehner J, Horton LE, Pfeffer MA, Longhurst CA, Schooley RT, Currier JS, et al. SARS-CoV-2 Infection after Vaccination in Health Care Workers in California. N Engl J Med. 2021;384(18):1774–5. Aliyari R, Mahdavi S, Enayatrad M, Sahab-Negah S, Nili S, Fereidooni M, et al. Study protocol: cohort event monitoring for safety signal detection after vaccination with COVID-19 vaccines in Iran. BMC Public Health. 2022;22(1):1153. Jara A, Undurraga EA, Gonzalez C, Paredes F, Fontecilla T, Jara G, et al. Effectiveness of an Inactivated SARS-CoV-2 Vaccine in Chile. N Engl J Med. 2021;385(10):875–84. Bernal JL, Andrews N, Gower C, Robertson C, Stowe J, Tessier E, et al. Effectiveness of the Pfizer-BioNTech and Oxford-AstraZeneca vaccines on covid-19 related symptoms, hospital admissions, and mortality in older adults in England: test negative case-control study. bmj. 2021;373. Haas EJ, Angulo FJ, McLaughlin JM, Anis E, Singer SR, Khan F, et al. Impact and effectiveness of mRNA BNT162b2 vaccine against SARS-CoV-2 infections and COVID-19 cases, hospitalisations, and deaths following a nationwide vaccination campaign in Israel: an observational study using national surveillance data. Lancet. 2021;397(10287):1819–29. Katikireddi SV, Cerqueira-Silva T, Vasileiou E, Robertson C, Amele S, Pan J, et al. Two-dose ChAdOx1 nCoV-19 vaccine protection against COVID-19 hospital admissions and deaths over time: a retrospective, population-based cohort study in Scotland and Brazil. Lancet. 2022;399(10319):25–35. Pouwels KB, Pritchard E, Matthews PC, Stoesser N, Eyre DW, Vihta KD, et al. Effect of Delta variant on viral burden and vaccine effectiveness against new SARS-CoV-2 infections in the UK. Nat Med. 2021;27(12):2127–35. Shrotri M, Navaratnam AM, Nguyen V, Byrne T, Geismar C, Fragaszy E, et al. Spike-antibody waning after second dose of BNT162b2 or ChAdOx1. The Lancet. 2021;398(10298):385–7. Hall VJ, Foulkes S, Saei A, Andrews N, Oguti B, Charlett A, et al. COVID-19 vaccine coverage in health-care workers in England and effectiveness of BNT162b2 mRNA vaccine against infection (SIREN): a prospective, multicentre, cohort study. Lancet. 2021;397(10286):1725–35. Hosseinzadeh A, Sahab-Negah S, Nili S, Aliyari R, Goli S, Fereidouni M, et al. COVID-19 cases, hospitalizations and deaths after vaccination: a cohort event monitoring study, Islamic Republic of Iran. Bull World Health Organ. 2022;100(8):474–83. V Shah AS, Gribben C, Bishop J, Hanlon P, Caldwell D, Wood R, et al. Effect of vaccination on transmission of COVID-19: an observational study in healthcare workers and their households. medRxiv. 2021:2021.03. 11.21253275. Paris C, Perrin S, Hamonic S, Bourget B, Roue C, Brassard O, et al. Effectiveness of mRNA-BNT162b2, mRNA-1273, and ChAdOx1 nCoV-19 vaccines against COVID-19 in healthcare workers: an observational study using surveillance data. Clin Microbiol Infect. 2021;27(11):1699 e5- e8. Voysey M, Clemens SAC, Madhi SA, Weckx LY, Folegatti PM, Aley PK, et al. Safety and efficacy of the ChAdOx1 nCoV-19 vaccine (AZD1222) against SARS-CoV-2: an interim analysis of four randomised controlled trials in Brazil, South Africa, and the UK. Lancet. 2021;397(10269):99–111. Vokó Z, Kiss Z, Surján G, Surján O, Barcza Z, Pályi B, et al. Nationwide effectiveness of five SARS-CoV-2 vaccines in Hungary—the HUN-VE study. Clinical Microbiology and Infection. 2022;28(3):398–404. Pritchard E, Matthews PC, Stoesser N, Eyre DW, Gethings O, Vihta KD, et al. Impact of vaccination on new SARS-CoV-2 infections in the United Kingdom. Nat Med. 2021;27(8):1370–8. Logunov DY, Dolzhikova IV, Shcheblyakov DV, Tukhvatulin AI, Zubkova OV, Dzharullaeva AS, et al. Safety and efficacy of an rAd26 and rAd5 vector-based heterologous prime-boost COVID-19 vaccine: an interim analysis of a randomised controlled phase 3 trial in Russia. Lancet. 2021;397(10275):671–81. AlHosani FI, Stanciole AE, Aden B, Timoshkin A, Najim O, Zaher WA, et al. Impact of the Sinopharm’s BBIBP-CorV vaccine in preventing hospital admissions and death in infected vaccinees: Results from a retrospective study in the emirate of Abu Dhabi, United Arab Emirates (UAE). Vaccine. 2022;40(13):2003–10. Additional Declarations No competing interests reported. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7289111","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":499470496,"identity":"04135497-6fc6-45d4-a96f-67998c787821","order_by":0,"name":"Sepideh Mahdavi","email":"","orcid":"","institution":"Iran University of Medical Sciences","correspondingAuthor":false,"prefix":"","firstName":"Sepideh","middleName":"","lastName":"Mahdavi","suffix":""},{"id":499470497,"identity":"8ac3279c-ac40-4d99-8463-ef5f86a52924","order_by":1,"name":"Mostafa Enayatrad","email":"data:image/png;base64,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","orcid":"","institution":"Shahroud University of Medical Sciences","correspondingAuthor":true,"prefix":"","firstName":"Mostafa","middleName":"","lastName":"Enayatrad","suffix":""},{"id":499470498,"identity":"cab2e09a-8532-460c-bf3e-3996aa6997bf","order_by":2,"name":"Shahrbanoo Goli","email":"","orcid":"","institution":"Shahroud University of Medical Sciences","correspondingAuthor":false,"prefix":"","firstName":"Shahrbanoo","middleName":"","lastName":"Goli","suffix":""},{"id":499470499,"identity":"df422436-3922-4a0a-a901-d3d370f35417","order_by":3,"name":"Fariba Zare","email":"","orcid":"","institution":"Iran University of Medical Sciences","correspondingAuthor":false,"prefix":"","firstName":"Fariba","middleName":"","lastName":"Zare","suffix":""}],"badges":[],"createdAt":"2025-08-04 09:08:21","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7289111/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7289111/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":89279931,"identity":"f6781679-3b31-4de5-8315-2ee4c08e4ebf","added_by":"auto","created_at":"2025-08-18 10:21:00","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1186056,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7289111/v1/8f39511e-7703-40c3-85c5-e0d079e7f920.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Effectiveness of COVID-19 Vaccines against SARS-CoV-2 Infection in a Healthcare Worker Cohort: A Prospective Study","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe COVID-19 pandemic represents one of the most significant global health crises of the 21st century, affecting billions of people worldwide and causing profound disruptions to daily life while imposing substantial financial burdens on healthcare systems (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e). Non-pharmaceutical interventions (NPIs), including social distancing, mask mandates, and contact tracing, were initially deployed as primary control strategies and effectively reduced transmission rates (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e). The rapid development and global deployment of vaccines subsequently marked a critical turning point in pandemic control, significantly reducing severe disease, hospitalizations, and mortality (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eVaccination remains one of the most effective and cost-efficient public health interventions for preventing and controlling infectious diseases, particularly during pandemics (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e). The rapid development and deployment of safe and efficacious COVID-19 vaccines represented a pivotal milestone toward ending the pandemic (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e). However, despite widespread vaccine distribution, ongoing evaluation of vaccine effectiveness is crucial to understanding both the benefits and potential adverse effects of vaccination programs. Multiple studies have demonstrated that vaccine effectiveness against SARS-CoV-2 infection wanes over time, with a pronounced decline observed against emerging variants such as Omicron (\u003cspan additionalcitationids=\"CR11\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eIn Iran, the National COVID-19 Headquarters prioritized high-risk groups, such as healthcare workers, elderly individuals, and individuals with underlying conditions for receiving the vaccine. This prioritization was implemented in most countries around the world to provide vaccines to people at risk (\u003cspan additionalcitationids=\"CR14\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e). In this context, various vaccines, such as AZD1222 (AstraZeneca), Sinopharm, and Sputnik V, have been used in Iran. The effectiveness of these vaccines has been reported in different global studies depending on the type of platform, storage conditions, and type of circulating strains; for example, the effectiveness of AstraZeneca in the UK was reported to be approximately 70%, and inactivated Chinese vaccines varied from 50\u0026ndash;90% (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e). Recent studies have shown that even during Omicron waves, receiving a booster dose increases vaccine effectiveness among healthcare workers (\u003cspan additionalcitationids=\"CR19\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e). Additionally, CDC reports from the United States indicated that mRNA vaccines were up to 90% effective in preventing infection, both symptomatic and asymptomatic (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eHealthcare workers (HCWs) face an elevated risk of contracting viral infections due to their direct and frequent contact with patients and clinical environments. Moreover, they may serve as vectors, transmitting the virus to other vulnerable populations within the community (\u003cspan additionalcitationids=\"CR24\" citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e). According to the World Health Organization (WHO), the HCW group includes physicians, nurses, laboratory technicians, support staff, and healthcare facility administrators (\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e). A systematic review estimated that approximately 3.9% of global COVID-19 cases occurred among HCWs. In contrast, a study conducted in Iran reported a substantially higher proportion, with 5.62% of infections observed in this group (\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e). Therefore, effective vaccination of this group not only supports their personal health but also contributes to reducing the transmission of the disease within the broader community. However, differences in vaccine acceptance, health literacy, access to healthcare services, and even cultural beliefs across regions may influence the effectiveness of vaccination efforts. Despite numerous international studies (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e), there is still insufficient evidence regarding the effectiveness of COVID-19 vaccines among Iranian healthcare workers, particularly at the regional level. Therefore, the present study aimed to evaluate the effectiveness of different COVID-19 vaccines in preventing SARS-CoV-2 infection among healthcare workers at Shahroud University of Medical Sciences.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cp\u003e\u003cb\u003eData collection and vaccination protocol\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThis study is a cohort study conducted among HCWs at Shahroud University of Medical Sciences in northeastern Iran. In this investigation, HCWs employed in various departments of hospitals, health centers, and administrative sections of Shahroud University of Medical Sciences were enrolled. Eligibility criteria included having received at least one dose of any of the following vaccines: AZD1222, Sinopharm (BBIBP-CorV), and Sputnik V, with their vaccination data registered in the Comprehensive COVID-19 Information Center.\u003c/p\u003e\u003cp\u003eAccording to the protocol established by the Center for Disease Management (CEM) in Iran (\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e), the Comprehensive COVID-19 Information Database was initiated in March 2020, coinciding with the onset of the COVID-19 pandemic. This database systematically records comprehensive information for all diagnosed individuals, including HCWs. The recorded data included RT‒PCR test results, CT scan findings, demographic information, treatment progression, and disease outcomes. Furthermore, with the commencement of HCW vaccination in April 2021, relevant vaccination data were also integrated into this database. For each HCW who was willing to be vaccinated, and on the basis of the Ministry of Health guidelines and vaccine availability, one of the three vaccines, AZD1222, Sinopharm (BBIBP-CorV), or Sputnik V, was administered.\u003c/p\u003e\u003cp\u003e\u003cb\u003eExposures and Outcomes\u003c/b\u003e\u003c/p\u003e\u003cp\u003eTo evaluate vaccine effectiveness, exposure period was considered a time-dependent variable. Individual exposure was categorized on the basis of vaccine status and type: unvaccinated (no exposure), one-dose vaccinated, two-dose vaccinated, and three-dose vaccinated. Given that vaccination has occurred over time, individuals have transitioned between groups, and their membership in each group has changed accordingly. Consequently, by the end of the study, with all individuals having received at least one vaccine dose, no participant remained in the unvaccinated group.\u003c/p\u003e\u003cp\u003eThe study groups were defined as follows:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eThe partial immunity group: included individuals who had received at least one dose of any vaccine type and were followed from 14 days after the first dose until 14 days after the second dose.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eThe full immunity group: included individuals who had received two doses of any vaccine type and were followed from 14 days after the second dose until 14 days after the third dose.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eThe Booster Immunity group: This group consisted of individuals who had received three doses of any vaccine type and were followed from 14 days after the third dose until the end of the study.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eThe primary outcome investigated in this study was confirmed COVID-19 infection (diagnosed via RT‒PCR). For this purpose, data on disease incidence among healthcare workers were retrieved from the Comprehensive COVID-19 Management System. The primary criterion for determining disease acquisition in this design was a positive RT‒PCR diagnostic test.\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eStatistical analysis\u003c/h2\u003e\u003cp\u003eThe incidence rate was calculated per 100,000 person-time, along with its 95% confidence interval (95% CI), across specific time intervals. These intervals included periods from 14 days post-receipt of one vaccine dose until 14 days post-receipt of the next dose. For the third dose, this calculation extended from 14 days after the third dose was received until the study's end (May 20, 2022). Vaccination status was defined as a categorical variable. To estimate the adjusted hazard ratios (HRs) for COVID-19 infection, we employed an extended Cox regression model. In this model, vaccine status was treated as a time-dependent variable, and calendar time served as the timescale. Finally, within the Cox models, adjusted hazard ratios (HRs) with their 95% CIs were reported for sex, age, workplace, type of work activity, and vaccine dose received.\u003c/p\u003e\u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eBetween April 4, 2021, and May 20, 2022, a total of 3365 individuals participated in the present study. All participants had received at least one dose of the vaccine under investigation. Of these, 95.3% had received at least two doses, and 36.7% of those who had received two doses also received a third dose of one of the available COVID-19 vaccines. Table 1 shows the distribution of participants by vaccination status, vaccine brand, demographic characteristics such as age and sex, and sector of activity.\u003c/p\u003e\n\u003cdiv\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"510\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"4\" valign=\"top\" style=\"width: 510px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTable 1: Characteristics of Study Participants by Vaccination Dose Received\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 162px;\"\u003e\n \u003cdiv align=\"right\"\u003e\n \u003ctable dir=\"rtl\" border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"148\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 148px;\"\u003e\n \u003cp dir=\"LTR\"\u003e\u003cstrong\u003eVariable\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 110px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eOne Dose Received\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 114px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTwo Dose Received\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 124px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eThree Dose Received\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 162px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eEnrollment start date\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 110px;\"\u003e\n \u003cp\u003e04 April 2021\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 114px;\"\u003e\n \u003cp\u003e09 March 2021\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 124px;\"\u003e\n \u003cp\u003e19 September 2021\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 162px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eParticipants, n (%)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 110px;\"\u003e\n \u003cp\u003e3365 (100.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 114px;\"\u003e\n \u003cp\u003e3207 (95.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 124px;\"\u003e\n \u003cp\u003e1177 (36.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 162px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eAge (years), Mean (SD)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 110px;\"\u003e\n \u003cp\u003e34.71 (11.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 114px;\"\u003e\n \u003cp\u003e34.97 (11.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 124px;\"\u003e\n \u003cp\u003e37.60 (11.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 162px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSex, n (%)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 110px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 114px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 124px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 162px;\"\u003e\n \u003cp\u003eMales\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 110px;\"\u003e\n \u003cp\u003e1355 (40.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 114px;\"\u003e\n \u003cp\u003e1297 (40.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 124px;\"\u003e\n \u003cp\u003e489 (41.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 162px;\"\u003e\n \u003cp\u003eFemales\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 110px;\"\u003e\n \u003cp\u003e2010 (59.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 114px;\"\u003e\n \u003cp\u003e1910 (59.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 124px;\"\u003e\n \u003cp\u003e688 (58.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 162px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eStaff Group,\u003c/strong\u003e \u003cstrong\u003en (%)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 110px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 114px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 124px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 162px;\"\u003e\n \u003cp\u003eHospital\u003csup\u003e\u0026nbsp;a\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 110px;\"\u003e\n \u003cp\u003e1413 (42.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 114px;\"\u003e\n \u003cp\u003e1340 (41.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 124px;\"\u003e\n \u003cp\u003e515 (43.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 162px;\"\u003e\n \u003cp\u003eHealth services\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 110px;\"\u003e\n \u003cp\u003e398 (11.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 114px;\"\u003e\n \u003cp\u003e369 (11.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 124px;\"\u003e\n \u003cp\u003e139 (11.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 162px;\"\u003e\n \u003cp\u003eAdministrative b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 110px;\"\u003e\n \u003cp\u003e1554 (46.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 114px;\"\u003e\n \u003cp\u003e1498 (46.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 124px;\"\u003e\n \u003cp\u003e523 (44.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 162px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eWorkplace,\u003c/strong\u003e \u003cstrong\u003en (%)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 110px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 114px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 124px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 162px;\"\u003e\n \u003cp\u003eHospital staff\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 110px;\"\u003e\n \u003cp\u003e1925 (57.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 114px;\"\u003e\n \u003cp\u003e1874 (58.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 124px;\"\u003e\n \u003cp\u003e744 (63.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 162px;\"\u003e\n \u003cp\u003eHealth centers\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 110px;\"\u003e\n \u003cp\u003e240 (7.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 114px;\"\u003e\n \u003cp\u003e219 (6.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 124px;\"\u003e\n \u003cp\u003e85 (7.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 162px;\"\u003e\n \u003cp\u003eAdministrative centers\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 110px;\"\u003e\n \u003cp\u003e1200 (35.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 114px;\"\u003e\n \u003cp\u003e1114 (34.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 124px;\"\u003e\n \u003cp\u003e348 (29.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 162px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eVaccine\u003c/strong\u003e, \u003cstrong\u003en (%)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 110px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 114px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 124px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 162px;\"\u003e\n \u003cp\u003eAZD1222\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 110px;\"\u003e\n \u003cp\u003e1654 (49.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 114px;\"\u003e\n \u003cp\u003e1555 (48.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 124px;\"\u003e\n \u003cp\u003e960 (81.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 162px;\"\u003e\n \u003cp\u003eSinopharm\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 110px;\"\u003e\n \u003cp\u003e578 (17.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 114px;\"\u003e\n \u003cp\u003e534 (16.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 124px;\"\u003e\n \u003cp\u003e120 (10.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 162px;\"\u003e\n \u003cp\u003eSputnik V\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 110px;\"\u003e\n \u003cp\u003e1133 (33.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 114px;\"\u003e\n \u003cp\u003e1118 (34.9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 124px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 162px;\"\u003e\n \u003cp\u003eOther\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 110px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 114px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 124px;\"\u003e\n \u003cp\u003e97 (8.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"4\" valign=\"top\" style=\"width: 510px;\"\u003e\n \u003col\u003e\n \u003cli\u003eHospital staff: Includes doctors, nurses, and other medical personnel directly working in hospitals.\u003c/li\u003e\n \u003cli\u003eadministrative: Refers to nonclinical or management staff within the healthcare system.\u003c/li\u003e\n \u003c/ol\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eThe incidence rate of COVID-19 among vaccinated individuals was 42.65 (95% CI: 39.12 to 46.49) per 100,000 person-days. Based on vaccine brand, the incidence rate in recipients of the AstraZeneca vaccine was 40.55 (95% CI: 36.38-45.20), that of the Sinopharm vaccine was 33.58 (95% CI: 26.43-42.66), and that of the Sputnik V vaccine was 55.57 (95% CI: 48.86-63.21) per 100,000 person-days. Regardless of vaccine brand, the incidence rate was significantly higher in females, individuals aged 18-49 years, health services staff, and those working in health centers. Table 2 reports these rates stratified by vaccine brand, sex, age group, workplace, and the incidence rate of COVID-19 among individuals who had received a third vaccine dose was higher than that among those who had received one or two doses of any vaccine brand, regardless of the specific brand. Furthermore, for each received dose, the incidence rate was consistently higher in females than in males, higher in health service staff than in other occupational groups, and higher in those working in health centers than in other workplaces.\u003c/p\u003e\n\u003cp\u003eHowever, the incidence rate in the 18-49 years age group after receiving the first dose was lower than that in the over 50 years age group, whereas it was higher in the 18-49 years age group after receiving the second and third doses. The incidence of COVID-19 was significantly higher after the first dose of the AZ1222 vaccine (30.50% CI: 23.42-39.73), after the second dose of the Sputnik V vaccine (54.29% CI: 46.41-63.52), and after the third dose of the AZ1222 vaccine (72.27% CI: 59.80-89.79). Table 3 shows the incidence rates in vaccine recipients based on each dose received and the variables of sex, age, place of work, and type of work.\u003c/p\u003e\n\u003cdiv\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"450\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"3\" style=\"width: 450px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTable 2\u003c/strong\u003e\u003cstrong\u003e. Incidence Rate of COVID-19 Cases per 100,000 Person-Days (95% CI)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 204px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003csub\u003eVariable\u003c/sub\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003csub\u003eNumber of Events (n)\u003c/sub\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 147px;\"\u003e\n \u003cp\u003eIncidence Rate (95% CI) \u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 204px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eVaccine Brand\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003csub\u003e\u0026nbsp;\u003c/sub\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 147px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 204px;\"\u003e\n \u003cp\u003eOverall Vaccine\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003e517\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 147px;\"\u003e\n \u003cp\u003e42.65 (39.12-46.49)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 204px;\"\u003e\n \u003cp\u003eAZ1222\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003e326\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 147px;\"\u003e\n \u003cp\u003e40.55 (36.38-45.20)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 204px;\"\u003e\n \u003cp\u003eSinopharm\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003e67\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 147px;\"\u003e\n \u003cp\u003e33.58 (26.43-42.66)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 204px;\"\u003e\n \u003cp\u003eSputnik V\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003e232\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 147px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e55.57 (48.86-63.21)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 204px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSex\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 147px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 204px;\"\u003e\n \u003cp\u003eMales\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003e187\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 147px;\"\u003e\n \u003cp\u003e38.00 (32.93-43.86)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 204px;\"\u003e\n \u003cp\u003eFemales\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003e330\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 147px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e45.82 (41.13-51.04)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 204px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eAge Group\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 147px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 204px;\"\u003e\n \u003cp\u003e18-49 years\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003e460\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 147px;\"\u003e\n \u003cp\u003e43.42 (39.63-47.57)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 204px;\"\u003e\n \u003cp\u003e\u0026ge; 50 years\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003e57\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 147px;\"\u003e\n \u003cp\u003e39.42 (30.41-51.11)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 204px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eStaff Group\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 147px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 204px;\"\u003e\n \u003cp\u003eHospital staff\u003csup\u003e\u0026nbsp;b\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003e341\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 147px;\"\u003e\n \u003cp\u003e48.83 (43.91-54.30)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 204px;\"\u003e\n \u003cp\u003eHealth services\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003e50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 147px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e58.64 (44.44-77.37)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 204px;\"\u003e\n \u003cp\u003eAdministrative centers \u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003e126\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 147px;\"\u003e\n \u003cp\u003e29.39 (24.68-35.00)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 204px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eWorkplace\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 147px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 204px;\"\u003e\n \u003cp\u003eHospital\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003e278\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 147px;\"\u003e\n \u003cp\u003e54.95 (48.85-61.80)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 204px;\"\u003e\n \u003cp\u003eHealth centers\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003e81\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 147px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e56.78 (45.66-70.59)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 204px;\"\u003e\n \u003cp\u003eAdministrative centers\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003e158\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 147px;\"\u003e\n \u003cp\u003e28.03 (23.98-32.76)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"3\" style=\"width: 450px;\"\u003e\n \u003col\u003e\n \u003cli\u003eIncidence, cases per 100 000 person-days (95% CI)\u003c/li\u003e\n \u003cli\u003eHospital staff: Includes doctors, nurses, and other medical personnel directly working in hospitals.\u003c/li\u003e\n \u003cli\u003eadministrative: Refers to nonclinical or management staff within the healthcare system\u003c/li\u003e\n \u003c/ol\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"725\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"7\" style=\"width: 725px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTable 3. \u0026nbsp;Incidence Rate of COVID-19 Infection by Vaccination Dose and Subgroup Characteristics\u003c/strong\u003e\u003c/p\u003e\n \u003ctable border=\"0\" cellspacing=\"3\" cellpadding=\"0\"\u003e\n \u003cthead\u003e\u003c/thead\u003e\n \u003c/table\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 209px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003csub\u003eVariable\u003c/sub\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 166px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eOne Dose Received\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 174px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTwo Dose Received\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 176px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eThree Dose Received\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003csub\u003eEvent (n)\u003c/sub\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003eIncidence Rate (95% CI) \u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003csub\u003eEvent\u003c/sub\u003e\u003c/strong\u003e\u003cstrong\u003e\u003csub\u003e\u0026nbsp;(n)\u003c/sub\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003eIncidence Rate (95% CI)\u003cstrong\u003e\u003csub\u003e\u0026nbsp;\u003c/sub\u003e\u003c/strong\u003e\u003cstrong\u003e\u003csup\u003ea\u003c/sup\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 39px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003csub\u003eEvent (n)\u003c/sub\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 137px;\"\u003e\n \u003cp\u003eIncidence Rate (95% CI)\u003cstrong\u003e\u0026nbsp;\u003csup\u003ea\u003c/sup\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 209px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eAny Vaccine\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 209px;\"\u003e\n \u003cp\u003eMales\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e27.13 (18.73-39.29)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e122\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e38.04 (31.86-45.43)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e36\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e55.65 (40.14-77.15)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eFemales\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e28.61 (21.36-38.33)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e216\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e45.87 (40.15-52.42)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e69\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e78.52 (62.02-99.42)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003e18-49 years\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e62\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e26.46 (20.63-33.94)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e309\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e44.39 (39.70-49.62)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e88\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e72.02 (58.44-88.76)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003e\u0026ge; 50 years\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e44.81 (24.82-80.93)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e32.19 (22.37-46.32)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e58.46 (36.34-94.04)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eHospital staff\u003csup\u003e\u0026nbsp;b\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e33.19 (24.78-44.45)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e221\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e48.28 (42.32-55.09)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e75\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e75.32 (60.07-94.45)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eHealth services staff\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e49.96 (27.67-90.22)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e57.28 (40.05-81.92)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e76.98 (38.49-153.93)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eAdministrative staff \u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e16.52 (10.27-26.58)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e87\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e30.91 (25.05-38.144)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e51.64 (34.00-78.44)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eWorking in hospital\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e27.41 (18.93-39.71)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e183\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e55.40 (47.93-64.04)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e67\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e96.70 (76.11-122.86)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eWorking in Health centers\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e54.66 (34.43-86.75)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e48\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e52.46 (39.53-69.61)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e80.03 (47.40-135.13)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eWorking in Administrative centers\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e21.53 (14.76-31.39)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e107\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e28.94 (23.94-34.98)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e36.48 (24.45-54.43)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eAfter receiving the dose\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e73\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e28.02 (22.28-35.25)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e338\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e42.70 (38.38-47.51)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e105\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e68.82 (56.84-83.33)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eAZ1222\u003c/strong\u003e \u003cstrong\u003eVaccine\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 209px;\"\u003e\n \u003cp\u003eMales\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e27.55 (17.77-42.71)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e30.97 (23.20-41.35)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e60.37 (42.92-84.92)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eFemales\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e32.49 (23.32-45.25)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e41.36 (33.64-50.86)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e83.03 (64.47-106.94)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003e18-49 years\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e27.65 (20.64-37.03)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e124\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e37.91 (31.79-45.20)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e79\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e79.25 (63.56-98.80)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003e\u0026ge; 50 years\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e59.40 (31.96-110.41)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e31.47 (17.87-55.41)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e53.97 (31.96-91.13)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eHospital staff\u003csup\u003e\u0026nbsp;b\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e34.12 (24.13-48.26)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e39.51 (31.90-48.93)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e67\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e76.25 (60.01-96.88)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eHealth services staff\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e54.51 (28.36-104.77)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e53.59 (31.74-90.50)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e83.22 (41.61-166.40)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eAnother staff \u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e19.99 (11.83-33.75)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e38\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e29.83 (21.71-41.00)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e61.14 (38.52-97.04)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eWorking in hospital\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e27.80 (17.28-44.72)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e52\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e45.61 (34.75-59.86)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e62\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e105.64 (82.36-135.50)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eWorking in Health centers\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e62.25 (37.52-103.25)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e59.17 (38.96-89.86)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e85.89 (50.87-145.03)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eWorking in Administrative centers\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e24.19 (16.07-36.40)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e62\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e28.85 (22.49-37.01)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e32.73 (20.35-52.66)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eAfter receiving the dose\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e55\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e30.50 (23.42-39.73)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e136\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e37.15 (31.40-43.95)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e93\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e72.27 (59.80-89.79)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSinopharm\u003c/strong\u003e \u003cstrong\u003eVaccine\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 209px;\"\u003e\n \u003cp\u003eMales\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e34.12 (12.80-90.91)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e33.88 (21.06-54.50)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e33.72 (8.43-134.85)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eFemales\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e20.64 (8.59-49.60)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e32.98 (22.92-47.46)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e60.00 (26.95-133.56)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003e18-49 years\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e25.71 (13.38-49.42)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e43\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e32.78 (24.31-44.21)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e49.37 (23.54-103.57)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003e\u0026ge; 50 years\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e45.16 (14.56-140.04)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e57.04 (8.03-404.96)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eHospital staff\u003csup\u003e\u0026nbsp;b\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e77.00 (36.71-161.53)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e53.54 (33.28-86.13)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e85.17 (31.96-226.95)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eHealth services staff\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e86.28 (21.57-94.88)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eAnother staff \u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e8.02 (2.00-32.08)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e25.95 (17.79-37.84)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e37.62 (14.12-100.25)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eWorking in hospital\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e34.82 (14.49-83.67)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e38.99 (25.16-60.44)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e46.38 (14.96-143.83)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eWorking in Health centers\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e73.85 (10.40-85.30)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e65.92 (16.48-69.57)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eWorking in Administrative centers\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e22.82 (15.29-34.04)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e28.64 (19.19-42.73)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e56.74 (23.61-136.32)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eAfter receiving the dose\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e25.04 (13.03-48.12)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e33.30 (24.94-44.46)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e50.22 (25.11-100.42)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSputnik V Vaccine\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 209px;\"\u003e\n \u003cp\u003eMales\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e21.15 (7.93-56.36)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e59\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e48.37 (37.47-62.43)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eFemales\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e19.76 (8.22-47.49)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e97\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e58.67 (48.08-71.58)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003e18-49 years\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e21.88 (10.94-43.75)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e142\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e59.70 (50.64-70.37)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003e\u0026ge; 50 years\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e14.71 (2.07-49.10)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e30.90 (18.30-52.17)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eHospital staff\u003csup\u003e\u0026nbsp;b\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e18.33 (8.23-40.82)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e120\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e56.24 (47.03-67.26)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eHealth services staff\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e55.89 (13.97-103.50)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e58.48 (34.64-98.75)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eAnother staff \u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e12.65 (1.78-89.80)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e43.98 (28.95-66.79)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eWorking in hospital\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e22.54 (10.12-50.17)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e111\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e67.26 (55.85-81.02)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eWorking in Health centers\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e26.73 (6.68-106.89)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e46.79 (31.36-69.82)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eWorking in Administrative centers\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e9.90 (1.39-70.28)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e29.57 (19.28-45.35)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 209px;\"\u003e\n \u003cp\u003eAfter receiving the dose\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 36px;\"\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e20.36 (10.59-39.13)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e156\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e54.29 (46.41-63.52)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 39px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 137px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"7\" style=\"width: 725px;\"\u003e\n \u003col\u003e\n \u003cli\u003eIncidence, cases per 100 000 person-days (95% CI)\u003c/li\u003e\n \u003cli\u003eHospital staff: Includes doctors, nurses, and other medical personnel directly working in hospitals.\u003c/li\u003e\n \u003cli\u003eadministrative: Refers to nonclinical or management staff within the healthcare system\u003c/li\u003e\n \u003c/ol\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eCox regression analysis revealed that the risk of disease was higher in females than in males, with an HR of 1.28 (95% CI: 1.07-1.54) for females compared with males. Furthermore, a significantly higher hazard ratio was observed in females who had received the AZD1222 vaccine. For every one-year increase in age, the hazard ratio increased. Compared with staff working in hospitals, staff working in health services and administrative sectors had hazard ratios of 0.96 (95% CI: 0.74-1.25) and 0.50 (95% CI: 0.74-1.22), respectively, indicating a lower risk of infection. Across all three periods of partial, full, and booster (or primary, secondary, and tertiary immunity phases of the vaccine), the AZD1222 vaccine demonstrated significantly better efficacy than the other vaccines did. Additionally, receiving three doses of any vaccine conferred increased immunity in individuals (Table 4).\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"678\" class=\"fr-table-selection-hover\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\" valign=\"top\" style=\"width: 678px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTable 4. Hazard Ratios\u003csup\u003e\u0026nbsp;a\u003c/sup\u003e for COVID-19 Infection by Vaccine Brand and Participant Characteristics\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 203px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003csub\u003eVariable\u003c/sub\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eAZD1222\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSinopharm\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSputnik V\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 135px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eany vaccine Received\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 203px;\"\u003e\n \u003cp\u003eSex: Female vs. Male\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e1.48 (1.11 \u0026ndash; 1.97)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e1.12 (0.65 \u0026ndash; 1.90)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e1.14 (0.88 \u0026ndash; 1.49)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 135px;\"\u003e\n \u003cp\u003e1.28 (1.07 \u0026ndash; 1.54)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 203px;\"\u003e\n \u003cp\u003eAge (per years increase)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e1.01 (0.99 \u0026ndash; 1.02)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e1.02 (1.00 \u0026ndash; 1.05)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e0.99 (0.98 \u0026ndash; 1.00)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 135px;\"\u003e\n \u003cp\u003e1.01 (1.00 \u0026ndash; 1.02)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 203px;\"\u003e\n \u003cp\u003e0\u0026ndash;13 days after first dose\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eRef\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eRef\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eRef\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 135px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eRef\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 203px;\"\u003e\n \u003cp\u003ePartial immunity b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e0.20 (0.09 \u0026ndash; 0.42)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e0.63 (0.08 \u0026ndash; 4.75)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e0.56 (0.11 \u0026ndash; 2.89)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 135px;\"\u003e\n \u003cp\u003e0.45 (0.20 \u0026ndash; 1.00)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 203px;\"\u003e\n \u003cp\u003eFull immunity\u003csup\u003e\u0026nbsp;c\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e0.11 (0.05 \u0026ndash; 0.22)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e0.45 (0.06 \u0026ndash; 3.18)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e0.64 (0.13 \u0026ndash; 3.20)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 135px;\"\u003e\n \u003cp\u003e0.36 (0.16 -0.79)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 203px;\"\u003e\n \u003cp\u003eBooster immunity \u003csup\u003ed\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e0.02 (0.01 -0.04)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e0.07 (0.01 \u0026ndash; 0.58)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e0.17 (0.03 \u0026ndash; 0.87)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 135px;\"\u003e\n \u003cp\u003e0.08 (0.03 \u0026ndash; 0.19)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 203px;\"\u003e\n \u003cp\u003eWorking in hospital\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eRef\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eRef\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eRef\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 135px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eRef\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 203px;\"\u003e\n \u003cp\u003eWorking in Health centers\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e1.91 (1.19 \u0026ndash; 3.05)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e1.13 (0.34 \u0026ndash; 3.73)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e0.56 (0.39 \u0026ndash; 0.82)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 135px;\"\u003e\n \u003cp\u003e0.96 (0.74 \u0026ndash; 1.25)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 203px;\"\u003e\n \u003cp\u003eWorking in Administrative centers\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e1.05 (0.69 \u0026ndash; 1.60)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e0.79 (0.44 \u0026ndash; 1.41)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e0.42 (0.31 \u0026ndash; 0.56)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 135px;\"\u003e\n \u003cp\u003e0.50 (0.74 \u0026ndash; 1.22)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\" valign=\"top\" style=\"width: 678px;\"\u003e\n \u003col\u003e\n \u003cli\u003eHazard Ratio in extended Cox regression model, with vaccine status as time- dependent variable and calendar time as the timescale by confidence interval 95%\u003c/li\u003e\n \u003cli\u003eDefined as the period between the 14th day after the first dose and 14 days after the second dose.\u003c/li\u003e\n \u003cli\u003eDefined as the period between the 14th day after the second dose and 14 days after the three doses.\u003c/li\u003e\n \u003cli\u003eDefined as the period between the 14th day after the three dose and the end of follow-up.\u003c/li\u003e\n \u003c/ol\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe present cohort study estimated that the overall effectiveness of COVID-19 vaccines among HCWs was 92% after receiving three vaccine doses. The effectiveness of the AZD1222, Sinopharm, and Sputnik V vaccines after three doses was estimated to be 98%, 93%, and 83%, respectively. These findings align with the results of effectiveness studies conducted on HCWs in England, Israel, and Chile, all of which reported favorable efficacy for COVID-19 vaccines (\u003cspan additionalcitationids=\"CR32\" citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e). Given the differences in vaccination strategies worldwide, it is important to evaluate the effectiveness of each vaccination program under different scenarios. Although the results obtained indicate sufficient protection from vaccines against COVID-19 infection, considering HCWs' high exposure risk to the virus, the gradual decline in immunity over time, and the emergence of new viral variants, this level of immunity could be further diminished. However, receiving three doses of each of the vaccines in the vaccination program may have been able to provide significant immunity against COVID-19 infection.\u003c/p\u003e\u003cp\u003eIn the present study, the incidence rate of COVID-19 significantly increased during the follow-up periods after the third and second doses compared with the first dose. This finding is consistent with results from a study on the AZD1222 vaccine in Scotland and Brazil (\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e), which also reported an increased incidence after the second dose. This increase in incidence could be attributed to several factors, including a decrease in vaccine effectiveness over time, an extended interval between doses, or shifts in viral variants. Furthermore, population-based studies in England and Wales indicated a decrease in antibody levels following the second dose of AZD1222. However, these studies still reported higher effectiveness in preventing disease acquisition (\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e). Importantly, in our study, individuals received their vaccinations at different times. Consequently, the occurrence of COVID-19 could be influenced by the timing of individuals' entry into the study and their duration of follow-up. Moreover, the emergence of newer viral variants over time (such as the delta and subsequently Omicron variants, which predominated during the study period) might lead to a reduction in vaccine effectiveness. Another crucial consideration is that the age and sex distributions of individuals vary by vaccine brand. Since the risk of infection differs on the basis of age and sex, a straightforward comparison of incidence rates solely on the basis of vaccine brand is not feasible. Therefore, to control for these confounding variables, Cox regression analysis was employed.\u003c/p\u003e\u003cp\u003eIn the present study, differences in the risk of disease after vaccination were observed across occupational groups. These differences suggest that other factors influencing the risk of infection among HCWs receiving a vaccination. These factors include time since vaccination, age, sex, dominant virus strain, severity of the epidemic, underlying diseases, and level of community attention to prevention programs. This finding is consistent with a vaccination study of HCWs in England (\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eIn the present study, the effectiveness of the AZD1222 vaccine was significantly higher than that of the other two vaccines in all three periods of partial, full and booster immunity. Notably, the effectiveness of the Sinopharm vaccine during the booster immunization period was somewhat comparable to that of the AZD1222 vaccine during the same period. Similar findings, particularly concerning the partial immunity period, have also been reported in a large multicenter study conducted in the Islamic Republic of Iran (\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe AZD1222 vaccine showed 89% effectiveness after two doses and 98% effectiveness after three doses. As previously mentioned, vaccine effectiveness is influenced by various factors. Consequently, these factors lead to discrepancies in reported studies. For instance, a study conducted in Scotland (\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e) on HCWs reported that the effectiveness of the AstraZeneca vaccine was 30% (95% CI: 22\u0026ndash;37%) 14 days after the first dose and 54% (95% CI: 30\u0026ndash;70%) 14 days after the second dose. In a study conducted in the UK (\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e) on HCWs, the effectiveness of the AstraZeneca vaccine was 56% and 62% at 28\u0026ndash;34 and 35\u0026ndash;48 days after receiving the vaccine, respectively. Furthermore, another study in France (\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e) on HCWs reported 86% and 100% effectiveness 14 days after receiving the first and second doses of the AstraZeneca vaccine, respectively. Moreover, in population-based studies, for example, a phase III clinical trial conducted on three continents revealed that the AstraZeneca vaccine was 70.4% effectiveness after two doses (\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e). Observational studies have also reported effectiveness rates ranging from 65\u0026ndash;86% after a single dose (\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e, \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e, \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eIn the present study, the effectiveness of the Sinopharm vaccine was reported to be 55% after two doses and 93% after three doses. In contrast, studies conducted in Hungary (\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e) and Chile (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e) reported effectiveness rates of 86.9% and 87.8%, respectively, after the second dose of this vaccine. The effectiveness of the Sputnik V vaccine was reported to be 44% after one dose and 36% after two doses. Notably, for booster doses among Sputnik V recipients, other vaccine types were utilized (as the third dose of Sputnik V was not available in Iran during the study period). This finding contrasts with the results of a phase III clinical trial, which reported a Sputnik V vaccine effectiveness of 85.7% one week after the second dose (\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e), and an observational study in Hungary (\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e) which reported 97.1% effectiveness after two doses. The Hungarian study (\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e) also reported that the AstraZeneca vaccine effectiveness at over 95%, and the Sinopharm vaccine effectiveness at 66.1%. Furthermore, a study in Abu Dhabi (\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e) indicated that the effectiveness of the Sinopharm vaccine was 80% in individuals who had received two doses. These discrepancies in vaccine effectiveness estimates across different studies can be attributed to various factors, including variations in study design; vaccination protocols employed; characteristics of the studied populations (e.g., prevalence, age, and underlying comorbidities); and variations in the duration of postvaccination follow-up and the number of doses administered.\u003c/p\u003e\u003cp\u003eThis study has several limitations. First, our effectiveness estimates focused solely on infections confirmed by PCR diagnostic tests. Other outcomes, such as hospitalization and mortality, were not evaluated in the final analysis because of their very low incidence within the study cohort during the investigation period. Second, we assessed the effectiveness against any SARS-CoV-2 infection and did not perform viral genome sequencing throughout the study period. This is particularly relevant, as B.1.617.2 (Delta) and subsequently Omicron variants became predominant during the study.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis study demonstrated that completing vaccination and receiving the second and third doses significantly increased vaccine effectiveness against SARS-CoV-2 infection. This enhanced efficacy played a crucial role in preventing SARS-CoV-2 infection among healthcare workers (HCWs). Among the vaccines investigated, vaccination with three doses of the AZD1222 vaccine showed the highest effectiveness.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was approved by the Ethics Committee of Shahroud University of Medical Sciences (approval number: IR.SHMU.REC.1400.076]).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used and/or analyzed during the current study are available from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was funded by Shahroud University of Medical Sciences. The funding body had no role in the design of the study, data collection, analysis, interpretation, or writing of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSM and ME conceptualized the study and contributed to the study design. ME and SHG were responsible for data collection and statistical analysis. FZ and SM wrote the initial draft of the manuscript. ME critically revised the manuscript and supervised the study. \u003cstrong\u003eME\u003c/strong\u003e contributed to the statistical analysis and interpretation of results All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors would like to thank all the staff of Shahroud University of Medical Sciences for their support during the study.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eGebru AA, Birhanu T, Wendimu E, Ayalew AF, Mulat S, Abasimel HZ, et al. Global burden of COVID-19: Situational analyis and review. Hum Antibodies. 2021;29(2):139\u0026ndash;48.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLevin AT, Owusu-Boaitey N, Pugh S, Fosdick BK, Zwi AB, Malani A, et al. Assessing the burden of COVID-19 in developing countries: systematic review, meta-analysis and public policy implications. 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Assessment of US Healthcare Personnel Attitudes Towards Coronavirus Disease 2019 (COVID-19) Vaccination in a Large University Healthcare System. Clin Infect Dis. 2021;73(10):1776\u0026ndash;83.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGala D, Parrill A, Patel K, Rafi I, Nader G, Zhao R, et al. Factors impacting COVID-19 vaccination intention among medical students. Human vaccines \u0026amp; immunotherapeutics. 2022;18(1):2025733.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eOgilvie GS, Gordon S, Smith LW, Albert A, Racey CS, Booth A, et al. Intention to receive a COVID-19 vaccine: results from a population-based survey in Canada. BMC Public Health. 2021;21(1):1017.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTerry E, Cartledge S, Damery S, Greenfield S. Factors associated with COVID-19 vaccine intentions during the COVID-19 pandemic; a systematic review and meta-analysis of cross-sectional studies. BMC Public Health. 2022;22(1):1667.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSherman SM, Sim J, Cutts M, Dasch H, Aml\u0026ocirc;t R, Rubin GJ, et al. COVID-19 vaccination acceptability in the UK at the start of the vaccination programme: a nationally representative cross-sectional survey (CoVAccS\u0026ndash;wave 2). Public health. 2022;202:1\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCreech CB, Walker SC, Samuels RJ. SARS-CoV-2 Vaccines. JAMA. 2021;325(13):1318\u0026ndash;20.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLu J, Wen X, Guo Q, Ji M, Zhang F, Wagner AL, et al. Sensitivity to COVID-19 Vaccine Effectiveness and Safety in Shanghai, China. Vaccines (Basel). 2021;9(5):472.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGaio V, Santos AJ, Amaral P, Viana JF, Antunes I, Pacheco V, et al. COVID-19 vaccine effectiveness among healthcare workers: a hospital-based cohort study. BMJ open. 2023;13(5):e068996.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRubin-Smith JE, Castro MYR, Preza I, Hasibra I, Sulo J, Fico A, et al. Primary series COVID-19 vaccine effectiveness among healthcare workers in Albania, February\u0026ndash;December 2021. IJID regions. 2023;8:19\u0026ndash;27.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSavulescu C, Prats-Uribe A, Brolin K, Lovrić Makarić Z, Uusk\u0026uuml;la A, Panagiotakopoulos G, et al. Incidence of SARS-CoV-2 infection among European healthcare workers and effectiveness of the first booster COVID-19 vaccine, VEBIS HCW observational cohort study, May 2021\u0026ndash;May 2023. Vaccines. 2024;12(11):1295.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFowlkes A. Effectiveness of COVID-19 vaccines in preventing SARS-CoV-2 infection among frontline workers before and during B. 1.617. 2 (Delta) variant predominance\u0026mdash;eight US locations, December 2020\u0026ndash;August 2021. MMWR Morbidity and Mortality Weekly Report. 2021;70.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGhosh S, Shankar S, Chatterjee K, Chatterjee K, Yadav AK, Pandya K, et al. COVISHIELD (AZD1222) VaccINe effectiveness among healthcare and frontline Workers of INdian Armed Forces: Interim results of VIN-WIN cohort study. medical journal armed forces india. 2021;77:S264-S70.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMutambudzi M, Niedzwiedz C, Macdonald EB, Leyland A, Mair F, Anderson J, et al. Occupation and risk of severe COVID-19: prospective cohort study of 120 075 UK Biobank participants. Occupational and environmental medicine. 2021;78(5):307\u0026ndash;14.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRhodes S, Wilkinson J, Pearce N, Mueller W, Cherrie M, Stocking K, et al. Occupational differences in SARS-CoV-2 infection: analysis of the UK ONS COVID-19 infection survey. J Epidemiol Community Health. 2022;76(10):841\u0026ndash;6.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBenenson S, Oster Y, Cohen MJ, Nir-Paz R. BNT162b2 mRNA Covid-19 vaccine effectiveness among health care workers. New England Journal of Medicine. 2021;384(18):1775\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWorld Health Organization. Working together for health: the world health report 2006. 2006.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBandyopadhyay S, Baticulon RE, Kadhum M, Alser M, Ojuka DK, Badereddin Y, et al. Infection and mortality of healthcare workers worldwide from COVID-19: a systematic review. BMJ Glob Health. 2020;5(12).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSabetian G, Moghadami M, Hashemizadeh Fard Haghighi L, Shahriarirad R, Fallahi MJ, Asmarian N, et al. COVID-19 infection among healthcare workers: a cross-sectional study in southwest Iran. Virology journal. 2021;18(1):58.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKeehner J, Horton LE, Pfeffer MA, Longhurst CA, Schooley RT, Currier JS, et al. SARS-CoV-2 Infection after Vaccination in Health Care Workers in California. N Engl J Med. 2021;384(18):1774\u0026ndash;5.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAliyari R, Mahdavi S, Enayatrad M, Sahab-Negah S, Nili S, Fereidooni M, et al. Study protocol: cohort event monitoring for safety signal detection after vaccination with COVID-19 vaccines in Iran. BMC Public Health. 2022;22(1):1153.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eJara A, Undurraga EA, Gonzalez C, Paredes F, Fontecilla T, Jara G, et al. Effectiveness of an Inactivated SARS-CoV-2 Vaccine in Chile. N Engl J Med. 2021;385(10):875\u0026ndash;84.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBernal JL, Andrews N, Gower C, Robertson C, Stowe J, Tessier E, et al. Effectiveness of the Pfizer-BioNTech and Oxford-AstraZeneca vaccines on covid-19 related symptoms, hospital admissions, and mortality in older adults in England: test negative case-control study. bmj. 2021;373.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHaas EJ, Angulo FJ, McLaughlin JM, Anis E, Singer SR, Khan F, et al. Impact and effectiveness of mRNA BNT162b2 vaccine against SARS-CoV-2 infections and COVID-19 cases, hospitalisations, and deaths following a nationwide vaccination campaign in Israel: an observational study using national surveillance data. Lancet. 2021;397(10287):1819\u0026ndash;29.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKatikireddi SV, Cerqueira-Silva T, Vasileiou E, Robertson C, Amele S, Pan J, et al. Two-dose ChAdOx1 nCoV-19 vaccine protection against COVID-19 hospital admissions and deaths over time: a retrospective, population-based cohort study in Scotland and Brazil. Lancet. 2022;399(10319):25\u0026ndash;35.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePouwels KB, Pritchard E, Matthews PC, Stoesser N, Eyre DW, Vihta KD, et al. Effect of Delta variant on viral burden and vaccine effectiveness against new SARS-CoV-2 infections in the UK. Nat Med. 2021;27(12):2127\u0026ndash;35.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eShrotri M, Navaratnam AM, Nguyen V, Byrne T, Geismar C, Fragaszy E, et al. Spike-antibody waning after second dose of BNT162b2 or ChAdOx1. The Lancet. 2021;398(10298):385\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHall VJ, Foulkes S, Saei A, Andrews N, Oguti B, Charlett A, et al. COVID-19 vaccine coverage in health-care workers in England and effectiveness of BNT162b2 mRNA vaccine against infection (SIREN): a prospective, multicentre, cohort study. Lancet. 2021;397(10286):1725\u0026ndash;35.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHosseinzadeh A, Sahab-Negah S, Nili S, Aliyari R, Goli S, Fereidouni M, et al. COVID-19 cases, hospitalizations and deaths after vaccination: a cohort event monitoring study, Islamic Republic of Iran. Bull World Health Organ. 2022;100(8):474\u0026ndash;83.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eV Shah AS, Gribben C, Bishop J, Hanlon P, Caldwell D, Wood R, et al. Effect of vaccination on transmission of COVID-19: an observational study in healthcare workers and their households. medRxiv. 2021:2021.03. 11.21253275.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eParis C, Perrin S, Hamonic S, Bourget B, Roue C, Brassard O, et al. Effectiveness of mRNA-BNT162b2, mRNA-1273, and ChAdOx1 nCoV-19 vaccines against COVID-19 in healthcare workers: an observational study using surveillance data. Clin Microbiol Infect. 2021;27(11):1699 e5- e8.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eVoysey M, Clemens SAC, Madhi SA, Weckx LY, Folegatti PM, Aley PK, et al. Safety and efficacy of the ChAdOx1 nCoV-19 vaccine (AZD1222) against SARS-CoV-2: an interim analysis of four randomised controlled trials in Brazil, South Africa, and the UK. Lancet. 2021;397(10269):99\u0026ndash;111.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eVok\u0026oacute; Z, Kiss Z, Surj\u0026aacute;n G, Surj\u0026aacute;n O, Barcza Z, P\u0026aacute;lyi B, et al. Nationwide effectiveness of five SARS-CoV-2 vaccines in Hungary\u0026mdash;the HUN-VE study. Clinical Microbiology and Infection. 2022;28(3):398\u0026ndash;404.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePritchard E, Matthews PC, Stoesser N, Eyre DW, Gethings O, Vihta KD, et al. Impact of vaccination on new SARS-CoV-2 infections in the United Kingdom. Nat Med. 2021;27(8):1370\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLogunov DY, Dolzhikova IV, Shcheblyakov DV, Tukhvatulin AI, Zubkova OV, Dzharullaeva AS, et al. Safety and efficacy of an rAd26 and rAd5 vector-based heterologous prime-boost COVID-19 vaccine: an interim analysis of a randomised controlled phase 3 trial in Russia. Lancet. 2021;397(10275):671\u0026ndash;81.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAlHosani FI, Stanciole AE, Aden B, Timoshkin A, Najim O, Zaher WA, et al. Impact of the Sinopharm\u0026rsquo;s BBIBP-CorV vaccine in preventing hospital admissions and death in infected vaccinees: Results from a retrospective study in the emirate of Abu Dhabi, United Arab Emirates (UAE). Vaccine. 2022;40(13):2003\u0026ndash;10.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"european-journal-of-medical-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ejmr","sideBox":"Learn more about [European Journal of Medical Research](http://eurjmedres.biomedcentral.com)","snPcode":"40001","submissionUrl":"https://submission.nature.com/new-submission/40001/3","title":"European Journal of Medical Research","twitterHandle":"@BioMedCentral","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"COVID-19 vaccines, Healthcare workers, Effectiveness","lastPublishedDoi":"10.21203/rs.3.rs-7289111/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7289111/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eIntroduction:\u003c/h2\u003e\u003cp\u003eA vaccine's ability to protect against disease acquisition is considered one of its most important aspects of effectiveness. The present study aimed to determine the effectiveness of COVID-19 vaccines among healthcare workers (HCWs).\u003c/p\u003e\u003ch2\u003eMaterials and Methods\u003c/h2\u003e\u003cp\u003eThis was a prospective cohort study conducted with HCWs from April 2021 to May 2022. We investigated the effectiveness of the AZD1222, Sinopharm, and Sputnik V vaccines against SARS-CoV-2 infection (diagnosed by PCR testing). For this purpose, vaccination data from 3365 HCWs were collected, and vaccine effectiveness was estimated via multivariable Cox models and the incidence rate of SARS-CoV-2 infection per 100,000 person-time.\u003c/p\u003e\u003ch2\u003eResult\u003c/h2\u003e\u003cp\u003eAmong the 3365 participants, all individuals received at least one dose, 95.3% received at least two doses, and 36.7% of those who received two doses also received three doses of the COVID-19 vaccine. The overall vaccine effectiveness after three doses was estimated to be 92% (95% confidence interval: 81\u0026ndash;97). The effectiveness of the AZD1222, Sinopharm, and Sputnik V vaccines after three doses was estimated to be 98% (95% confidence interval: 96\u0026ndash;97), 93% (95% confidence interval: 42\u0026ndash;99), and 83% (95% confidence interval: 13\u0026ndash;97), respectively.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e\u003cp\u003eThe results of this study indicate that completing vaccination and receiving second and third doses significantly increased vaccine effectiveness and was highly effective in preventing SARS-CoV-2 infection in HCWs. Furthermore, among the vaccines investigated, vaccination with three doses of the AZD1222 vaccine showed the highest effectiveness.\u003c/p\u003e","manuscriptTitle":"Effectiveness of COVID-19 Vaccines against SARS-CoV-2 Infection in a Healthcare Worker Cohort: A Prospective Study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-18 10:12:54","doi":"10.21203/rs.3.rs-7289111/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-01-22T11:55:23+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-21T10:59:01+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"334116930893029232133024662957409932020","date":"2026-01-20T08:15:57+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-17T10:36:41+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"206542128396593773866624910298568420473","date":"2026-01-17T10:13:57+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"135761069477051221951922162992368693946","date":"2026-01-16T10:05:55+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"130944377781808482176556863115381484448","date":"2026-01-16T01:31:59+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"113021811908472471181536018087013877823","date":"2026-01-15T23:09:41+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"306379699785823964128370115116423057696","date":"2026-01-15T08:36:40+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-12T12:21:27+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"150200832644397935014721019330861452911","date":"2025-09-11T05:00:42+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-08-10T14:39:04+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-08-06T05:44:47+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-08-05T12:37:03+00:00","index":"","fulltext":""},{"type":"submitted","content":"European Journal of Medical Research","date":"2025-08-04T08:55:28+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"european-journal-of-medical-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ejmr","sideBox":"Learn more about [European Journal of Medical Research](http://eurjmedres.biomedcentral.com)","snPcode":"40001","submissionUrl":"https://submission.nature.com/new-submission/40001/3","title":"European Journal of Medical Research","twitterHandle":"@BioMedCentral","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"a21d3a03-31fc-403d-af19-c1f233067ba9","owner":[],"postedDate":"August 18th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-02-26T14:12:18+00:00","versionOfRecord":[],"versionCreatedAt":"2025-08-18 10:12:54","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7289111","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7289111","identity":"rs-7289111","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}