Antibody Responses to SARS-Cov-2 among Health Care Workers of a Tertiary Hospital in North-Eastern, Tanzania

Background: Health Care Workers (HCWs) have been playing crucial role in treating patient with COVID- 19. They have a higher occupational risk of contracting the disease than the general population, and a greater chance of them transmitting the disease to vulnerable patients under their care. Given their scarcity and low COVID-19 vaccine acceptance in Africa, it is essential that HCWs are seroprotected and their exposure to COVID-19 minimized. This study was therefore designed to determine IgG antibody response to SARS-CoV- 2 among HCWs in North Eastern, Tanzania. Methodology: This was a cross -sectional study carried out among 273 HCWs at Kilimanjaro Christian Medical Centre (KCMC), a tertiary , zonal referral hospital in Tanzania's North Eastern region. Stratified sampling was used to select study participants. Data were obtained from each conse nting participant using a validated questionnaire. Blood samples were collected for SARS -CoV-2 IgG antibodies quantification by using an indirect ELISA test. RedCap software was used to enter and manage data. Statistical analysis was done by using STATA st atistical software version 15 and GraphPad Prism v 9.0 . A p -value of < 0.05 was considered the cut-off for statistical significance.

Among 273 HCWS only 37.9 % reported to have received COVID -19 vaccine. Except for one person, all of the participants had SARS-CoV-2 IgG antibody concentrations that were positive, with 64.5% of them having strong seropositivity. Female gender, allied health professionals, active smoking, COVID-19 patient interactions , COVID -19 vaccination receptivity, and adherence to recommended hand hygiene were found to be significant predictors of variation of median SARS-CoV-2 antibody concentration. The usage of personal protective equipment, history of previously testing PCR positive for COVI D-19, the number of COVID-19 patient exposure and age were found to cause no s ignificant variation in median antibo dy concentration among participants.

This study reports a high seropre valence of SARS -CoV-2 antibodies among healthcare workers in Kilimanjaro Christian Medical Ce ntre. This suggests that HCWs ha ve significant exposure to SARS-CoV-2 despite the low rate of vaccination acceptance even among HCWs. We recommend a strengthened Infectious Prevention and Control (IPC) in hospitals through provision of technical leadership and coordination according to WHO guidelines. We also recommend continued conduction of seroprevalence studies to estimate the magnitude and trends of SARS-CoV-2 infections in different populations in Tanzania. A better understanding of the past, current, and future transmission patterns of infectious pathogens is critical for preparedness and response planning, and to inform the optimal implementation of existing and novel interventions under the current and changing climate. Key words: SARS-CoV-2; COVID-19; immunoglobulin G; immunity; health care workers; vaccination . CC-BY-ND 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted April 12, 2024. ; https://doi.org/10.1101/2024.04.09.24305582doi: medRxiv preprint NOTE: This preprint reports new research that has not been certified by peer review and should not be used to guide clinical practice. 2 `

The novel corona virus disease 2019 (COVID-19), is caused by the Severe Acute Respiratory Syndrome Coronavirus 2 ( SARS-CoV-2)(1,2). COVID-19 has been a large-scale global threat since 2019 with high global morbidity and mortality rates associated with economic disabilities, and social disruptions (3–5). WHO had reported a total of 115,500 deaths of HCWs in the world due to COVID-19 based on population estimates (6). COVID-19 is affects primarily the respiratory system with potential effects in other body organs (1,7). In Tanzania, the first case of COVID-19 was reported in 2020 indicating the virus global spread and its impact (8). Health care personnel have been on the front lines in taking care of COVID-19 patients, thus exposed to a higher occupational risk of contracting the disease than the general population . To protect this vulnerable group, WHO had implemented several initiatives, including making COVID -19 vaccination a priority for HCWs. Nevertheless, there has been a considerably low COVID-19 vaccine acceptance in Africa due to concerns regarding safety and efficacy issues, and associated side effects of the vaccines(9). Immune responses to SARS-CoV- 2 are directed to t he four main structural proteins of the virus which are Spike (S), Envelope (E), Membrane (M), and Nucleocapsid (N) proteins (10). A specific humoral imm une response against N and S protein has been reported and tend to persist in individuals (11,12). Immune responses to t hese proteins could be a result of either natural immunity from infection or vaccination (13). However, It has been also been reported that p resence of neutralizi ng antibodies against these proteins correlates with the protection against future SARS- CoV-2 infection (14–16). There is limited information regarding SARS-Cov-2 immunity among HCWS in Africa. Since antibody response is an acceptable proxy indicator of exposure to an infectious agent, (17), monitoring SARS-CoV-2 antibody response provides important information regarding the burden of exposure to SARS-CoV-2 among the higher risk group of HCWs is important. A better understanding of the past, current, and future transmission patterns of infectious pathogens including emerging and re -emerging infections is critical for preparedness and response planning, and to inform the optimal implementation of existing and novel interventions under the current and changing climate. The current study was designed to assess the seroprevalence of SARS-CoV-2 IgG antibodies among HCWs with different demographics in North-Eastern, Tanzania. METHODOLOGY Study setting and design This was a cross sectional study, conducted from September to November, 2022. It was conducted in Kilimanjaro Christian Medical Centre, one of the four tertiary, zonal referral hospitals in Tanzania. It was purposively selected not only because it was a designed national center for managing COVID-19 cases during the pandemic but also its location in North-Eastern region of Tanzania. Kilimanjaro and Arusha are known for being the safari capitals of Tanzania, and popular stopovers for adventurers who are preparing for a Kilimanjaro trek. This makes Kilimanjaro region a vulnerable to cross border transmission of infectious diseases including SARS-CoV-2. Study population This study involved health care workers (HCWs) working at KCMC during the study period. Any person employed or volunteering in this setting was selected bas ed on the definition of a HCW by WHO (18). If the selected HCWs did not consent to participate or donate a blood sample, then they were considered as ineligible for the study and thus excluded. . CC-BY-ND 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted April 12, 2024. ; https://doi.org/10.1101/2024.04.09.24305582doi: medRxiv preprint 3 ` Sample Size and Sampling Technique As there was no prior data on the prevalence of SARS-COV-2 antibodies among HCWs during the design of the study and in order to have sufficient sample size, an estimate of 50% as seroprevalence of SARS COV- 2 antibodies among HCWs in Tanzania was considered. Using the formula by (19) and a desired precision of 0.05, and a confidence level of 0.95, a minimum sample size of 257 participants were required. However, to increase the power of analysis, 273 subjects were recruited in this study. To ensure fair healthcare workers' representation, the population of healthcare workers in KCMC hospital was divided into 13 strata. Thes e strata were represented by different hospital departments. Both inpatient and outpatient healthcare workers were selected from each stratum. Given the busy schedules and responsibilities of these healthcare workers, it was difficult to recruit them syste matically for the study in their strata; therefore, a convenience sample of no more than 38 healthcare employees from each stratum was selected. Data Collection procedures Healthcare workers who consented to participate in this study were interviewed by using the study questionnaire embedded in Redcap Software installed on an Android tablet. This was a validated tool by WHO Regional Office for Africa (AFRO) to be used for healthcare workers (20) . Because it was a guidance for SARS-COV-2 antibody screening among HCWs for cohort studies, only quest ions used for participant enrollment were asked in this study. This adapted questionnaire included socio demographic and clinical characteristics, information about COVID -19 vaccination history, and COVID -19 illness, occupation and community-related behaviour during the pandemic. Sample Collection From each study participant a total of 2 mls of blood sample through vein puncture were collected under aseptic condition. Samples were stored in a cooler box (maintained at 4-8°C) in the field for a maximum of 3 hours before these samples get transferred to the Biotechnology Laboratory at Kilimanjaro Christian Research Institute for serum extraction. The samples that were collected had instantly their serum extracted upon arrival at Biotechnology Laboratory at Ki limanjaro Christian Research Institute. For serum extraction, samples were allowed to clot then they were centrifuged at 1000 g for 15 minutes. After that, the serum was collected and kept frozen at negative 20°C. Detection of SARS-COV-2 Antibodies IgG antibodies against SARS-CoV-2 were detected by using Generic Assays (GA) Enzyme-Linked Immuno- Sorbent assay (ELISA) for SARS -CoV-2 IgG Screening kits (MedipanGmbHGA Generic Assays GmbH, Ludwig-Erhard-Ring 3, 15827 Blankenfelde-Mahlow OT Dahlewitz, Germany). This indirect ELISA kit was a two-stage that focuses on the Spike and Nucleocapsid antigen of the SARS -CoV-2 virus detection. .The reported sensitivity and specificity of these GA ELISA tests are > 98% (21). Statistical analysis STATA statistical software version 15 was used to do all statistical tests. Hence, all data from the created spreadsheet was imported to STATA. Descriptive statistics were employed to summarize the study participant's baseline socio-demographic, clinical, COVID-19 exposure history as well as the seroprevalence of antibodies against SARS- CoV-2. After verifying that SARS-CoV-2 IgG concentration among HCWs is not normally distributed (p =0.00132 by Shapiro Wilk test), non-parametric tests were performed to compare the significant difference between the exposure variables and median SARS -CoV-2 IgG concentration. The Mann–Whitney test was used for the comparison of antibody concentrations of two independent groups. The . CC-BY-ND 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted April 12, 2024. ; https://doi.org/10.1101/2024.04.09.24305582doi: medRxiv preprint 4 ` Kruskal–Wallis test was used for the comparison of more than two groups. A p-value of 0.05 was regarded as significant for the found associations Ethical Considerations. Ethical clearance to carry out this study was obtained from the College Research Ethical Committee (CREC) of Kilimanjaro Christian Medical University College (KCMUCo), ethical clearance number PG61/2022. Permission from the participant hospital administration was sought after the proposal was submitted and accepted by the ethical committee. To conceal participants' identities, the questionnaire and blood samples were labelled using numbers and letters.

Response rate A total of 273 of the 279 participants in this study had results on their serum SARS-CoV-2 IgG concentration, resulting in a rate of response of 97.8%. Demographic and Clinical-exposure Characteristics of the Study Participants Among the 273 participants, half of the participants were under 32 years old, with a median age of 32 (IQR: 26-44) and a male predominance of 60.4% among the total number of participants. The majority of study participants were nurses (40.5 %) and had a normal BMI (41.3%). Less than half of the study participants received the COVID-19 vaccine, and only 8.8% reported being tested PCR positive for COVID-19 in the past. The vast majority of participants (94.1%) stated that they had never smoked, Table 1. Table 1: Social demographic and clinical characteristics of the study participants (N=273) Variable Frequency Percentage Sex Male 165 60.4 Female 108 39.6 Age (in Years) *(n=272) ≤ 32 years 142 52.2 > 32 130 47.8 Median (IQR) 32 (26-44) Cadre*(n=268) Medical doctor 78 29.0 Nurse 109 40.5 Allied health professionals 58 21.6 Support staff 23 8.9 BMI*(n=267) Underweight 6 2.3 Normal 109 40.8 Overweight 83 31.1 Obesity 69 25.8 Median (IQR) 26.4(22.8-30.1) Smoking status Stopped >1 year ago 8 2.9 Never smoked 257 94.1 Currently smoke 8 3.0 Alcohol consumption Stopped >1 year ago 17 6.2 . CC-BY-ND 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted April 12, 2024. ; https://doi.org/10.1101/2024.04.09.24305582doi: medRxiv preprint 5 ` Never took alcohol 158 57.8 Currently take alcohol 98 36.0 Taking regular medication No 233 85.3 Yes 40 14.7 Tested PCR Positive for COVID-19*(n=272) No 248 91.2 Yes 24 8.8 Received COVID-19 vaccine*(n=272) No 169 62.1 Yes 103 37.9 * Indicates some missing values in respective variable Occupation and Community Related Behaviour Factors during the Pandemic Only 38.5% of the study participants wore mask at indoor setting outside their homes. A large proportion of participants (56.6%) practice good hand hygiene always as recommended, 38.9% follow IPC standard precautions when in contact with any patients, and fewer than half (42.4%) always wear PPE according to the risk assessment. Half of the study participant lived in a household size of 3-5 people and 39.5% used public transportation more than nine times a day, Table 2. Table 2: Behavioural characteristics of study participants (N=273) Variable Frequency Percentage Household size*(n=272) 1-2 people 90 33.1 3-5 people 136 50.0 6-8 people 37 13.6 9+ 9 3.3 Public transport None 75 27.5 1-2/day 68 24.9 3-5/day 19 7.0 6-8/day 3 1.1 9+/day 108 39.5 Stayed at least 2 meters from other people in indoor space*(n=273) Always 42 15.4 Did not go indoor location 31 11.4 Never 31 11.4 Often 28 10.2 Rarely 56 20.5 Sometimes 85 31.1 Hand hygiene practice*(n=265) Always as recommended 150 56.6 Most of the time 104 39.3 Never 3 1.1 Occasionally 8 3.0 IPC standards*(n=257) Always 100 38.9 . CC-BY-ND 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted April 12, 2024. ; https://doi.org/10.1101/2024.04.09.24305582doi: medRxiv preprint 6 ` I don't know what IPC standard precaution means 22 8.6 Most of the time 97 37.7 Never 2 0.8 Occasionally 28 10.9 Rarely 8 3.1 Wearing PPE as recommended*(n=264) Always 112 42.4 Most of the time 102 38.6 Never 8 3.1 Occasionally 33 12.5 Rarely 9 3.4 Interactions with COVID-19 Patients*(n=264) No 110 41.7 Yes 154 58.3 Exposure to COVID-19 Patients*(n=247) 1-10 Patients 169 68.4 11-50 41 16.6 51-100 18 7.3 101-500 17 6.9 > 500 2 0.8 *Indicates some missing values in respective variable Seroprevalence of SARS-CoV-2 IgG Antibody Concentration among the Study Participants Except for one person, all of the participants showed SARS-CoV-2 IgG antibody concentrations that were positive, with 64.5% of them having strong seropositivity, Figure 1. While comparing people who had received the COVID-19 vaccine and those who hadn't, it was shown that the majority of the vaccinated individuals had strong seropositivity, Figures 2 and 3. Negative Positve Strong Positive Weak Positive 0 20 40 60 80 100 5.1 64.5 30.0 0.4 Percentage of IgG seropositivity Figure 1: Seroprevalence of SARS-CoV-2 IgG antibody concentrations among the study participants (N=273) . CC-BY-ND 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted April 12, 2024. ; https://doi.org/10.1101/2024.04.09.24305582doi: medRxiv preprint 7 ` Negative Positve Strong Positive Weak Positive 0 20 40 60 80 7.7 58.6 33.1 0.6 Percentage of IgG seropositivity Figure 2: Seroprevalence of SARS-CoV-2 IgG antibody concentrations among non-vaccinated participants (N=169) Positve Srong Positive Weak Positive 0 20 40 60 80 100 1.0 73.8 25.2 Percentage of IgG seropositivity Figure 3: Seroprevalence of SARS-CoV-2 IgG antibody concentrations among vaccinated participants (N=103) Socio-Demographic, Clinical, a nd Behavioural Characteristics A ssociated with Variation in Median SARS-CoV-2 IgG Concentration among Study Participants. Sex, BMI, smoking status, adherence to recommended hand hygiene, cadre, and interaction with COVID-19 patients are variables that were found to significantly affect the median IgG concentration. IgG median concentration was significantly higher in females compared to males. It was found that those with obesity had significantly greater median concentrations than individuals with other BMI categories. Those who had . CC-BY-ND 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted April 12, 2024. ; https://doi.org/10.1101/2024.04.09.24305582doi: medRxiv preprint 8 ` never smoked had significantly higher SARS-CoV-2 IgG median concentrations than current smokers. Individuals, who followed recommended hand hygiene were found to significantly have a higher median concentration. Moreover, median concentrations were significantly greater in who interacted with COVID-19 patients. Interestingly, allied health proffessionals were found to have a significantly higher median concentration comparing to other health care workers. Other factors were assessed but found to not significantly causing differences in median SARSCOV 2 IgG concentration among participants, Figure 4. ≤ 32 years > 32 years 0 100 200 Age P-Value= 0.6567 IgG CONC (IU/ML) 127.257 128.228 Stopped > 1 year No alcohol Drinking alcohol 0 100 200 Alcohol consumption P-Value= 0.2500 IgG CONC (IU/ML) 116.338 128.588 127.413 A] IgG concentration by age Category B] IgG concentration by alcohol consumption Female Male 0 100 200 Sex P-value= 0.0261 IgG CONC (IU/ML) 130.054 121.183 No Yes 0 100 200 Interacting with COVID-19 patients P-value= 0.0232 IgG CONC (IU/ML) 125.116 131.070 . CC-BY-ND 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted April 12, 2024. ; https://doi.org/10.1101/2024.04.09.24305582doi: medRxiv preprint 9 ` C] IgG concentration by sex D] IgG concentration byCOVID-19 patient Interaction No Yes 0 100 200 Received COVID-19 vaccines P-Value= 0.0006 IgG CONC (IU/ML) 122.068 137.5 No Yes 0 100 200 Testing PCR Positive for COVID-19 P-Value= 0.1781 IgG CONC (IU/ML) 127.263 140.104 E] IgG concentration by receiving COVID-19 vaccine F] IgG concentration by testing positive for COVID- 19 Stopped > 1 year Never smoked Currently smoking 0 100 200 Smoking status P-Value= 0.0251 IgG CONC (IU/ML) 110.050 127.585 84.754 No Yes 0 100 200 Regular medication use P-Value= 0.1982 IgG CONC (IU/ML) 125.887 136.421 G] IgG concentration by Smoking status H] IgG concentration by regular medication use . CC-BY-ND 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted April 12, 2024. ; https://doi.org/10.1101/2024.04.09.24305582doi: medRxiv preprint 10 ` Underweight Normal Overweight Obese 0 100 200 BMI P-Value= 0.0455 IgG CONC (IU/ML) 114.275119.522 124.691 133.530 Doctors Nurses Allied Support 0 100 200 Cadre P-value= 0.0238 IgG CONC (IU/ML) 128.764 127.585 135.409 114.275 I] IgG concentration by BMI category J] IgG concentration by Cadre Categories 1-2 3-5 6-8 9+ 0 100 200 Household size P-value= 0.1234 IgG CONC (IU/ML) 121.875 132.662 118.326 138.719 None 1-2 3-5 6-8 9+ 0 100 200 Public transport use P-value= 0.529 IgG CONC (IU/ML) 125.247145.889 149.615 129.717 121.103 K] IgG concentration by household size L]IgG concentration by Public Transport use . CC-BY-ND 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted April 12, 2024. ; https://doi.org/10.1101/2024.04.09.24305582doi: medRxiv preprint 11 ` Always I don't know Most of time Never Occasionaly Rarely 0 100 200 P-value= 0.3625 Adherence to IPC standards IgG CONC (IU/ML) 131.790 125.803 125.320 129.717 121.103 130.200 1-10 11-50 51-100 101-500 > 500 0 100 200 COVID-19 pateint patient exposure P-value= 0.154 IgG CONC (IU/ML) 127.410 136.167 107.944 131.482 130.446 M] IgG concentration by adherence to IPC N] IgG concentration by COVID-19 pateint exposure Always Most of time Never Ocassionaly Rarely 0 100 200 PPE use P-value= 0.355 IgG CONC (IU/ML) 131.636124.424 110.983 122.068 127.585 Always Most of time Never Occasionally 0 100 200 Hand Hygiene Adherence P-value= 0.0048 IgG CONC (IU/ML) 128.800 127.837 149.615 89.307 O] IgG concentration by PPE USE P] IgG concentration by Hand Hygiene Adherence Figure 4: The median difference in IgG concentration among participants in different exposure groups. . CC-BY-ND 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted April 12, 2024. ; https://doi.org/10.1101/2024.04.09.24305582doi: medRxiv preprint 12 `

This study aimed at determining the IgG antibody response to SARS-CoV-2 among HCWs in our institution. The finding revealed a remarkably seroprevalence of 99 .6% among the sampled HCWs. Females, allied health professionals, obese people, HCWs who adhered to recommended hand hygiene practices, and those who interacted with COVID-19 patients more frequently had significantly higher median SARS-CoV- 2 antibody concentrations. Other factors that were assessed did not reveal any significant variation in Median SARS-CoV-2 IgG concentration. This higher seroprevalence of SARS-CoV-2 antibodies among HCWs indicates the high level of virus exposure in this population, and an existed risk of infection within the hospital. These results are also consistent with other studies that revealed high seroprevalence of SARS-CoV-2 antibodies among HCWs (22,23). However, this seroprevalence is higher than that reported in other East African countries (24–26). The l evel of COVID -19 pandemic precautions that was initially put in our country can explain this huge discrepancy with other East African countries. Contrary to the expectation, this study did not find any significant difference in antibody concentration between healthcare workers considering their previous history of testing PCR positive for COVID-19. This is contradicting finding to other previous studies that indicated that previous SARS-CoV-2 infection leads to higher SARS-CoV- 2 IgG antibodies concentrations (27–30). Several factors may have influenced these results. It might be due to the low percentage of healthcare workers who tested positive in this study. Also, the significant decline of SARS-CoV-2 antibody levels after infection may additionally explain this results (31). Hence, a time interval for antibody monitoring should be found so as to determine how long SARS -CoV-2 antibodies does lasts. Regarding various cadres, this study found that allied health professional had a higher SARS-CoV-2 median concentration compared to other HCWs. This indicate that there was an increased risk of SARS-CoV- 2 exposure among allied HCWS compared medical doctors and nursing cadres. Results are concordant with one previous observational study, which had shown increasing odds off seropositivity in allied health professionals compared to medical doctors (32). The reasons behind this finding are necessary to be explored in order to protect these allied HCWs from the risk of acquiring communicable diseases in their work setting Another important finding was a higher median antibody concentration among healthcare workers who adhere to recommended hand hygiene during the pandemic. The finding of our study does not support other studies that found no association between self-reported adherence to hand hygiene and SARS-CoV- 2 antibody positivity among HCWs (33). Hand hygiene is an important element of infection prevention practices in the hospital and reflects behavior, attitudes and beliefs (34). It may be hypothesized that HCWs who adhered to recommended hand hygiene were also more likely to receive COVI D-19 vaccine. However, this hypothesis was not explored in this study. Study finding has revealed that HCWs who interacted with COVID-19 patient had significantly higher median concentration. It is important to note that the number of COVID-19 patient the HCW is exposed to, does not predict seroconversion as per our study findings. Therefore, it confirms that COVID-19 patient exposure only is a significant factor for detecting SARS-CoV-2 antibodies among HCWs. These results match those observed in earlier studies that demonstrated that regular interaction with COVID-19 patients increases one's risk of contracting SARS-CoV-2 (27,35–39). It can be hypothesized that relying solely in number of COVID - 19 patient in hospitals led to inadequate HCWs protection. . CC-BY-ND 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted April 12, 2024. ; https://doi.org/10.1101/2024.04.09.24305582doi: medRxiv preprint 13 ` According to our findings, females had higher median concentrations of SARS-CoV-2 antibodies than males. This supports the theory that after disease exposure, females have higher antibody production compared to males because male androgens suppress the immune response (40). Contrary to our findings, several other studies have found that male HCWs have higher SARS -CoV-2 antibodies than female HCWs, inferring to behavioural differences (25,27,37,41,42). During the pandemic, male had a worse clinical outcomes and mortality (Kopel et al., 2020; O’Brien, Du and Peng, 2020). The argument can be that the immune response of female played a major role in Clinical outcome of COVID-19 rather than behavioural differences with males. The findings from this study indicate that individuals who currently smoke had a lower antibody response to SARS-CoV-2. This may be due to the fact that smoking increases the clearance of circulating antibodies by enhancing the production of monocytes and macrophages (43). It can also can be evidenced by the reduction of antibody titers after COVID -19 vaccination in individuals who smoke (44). However, some other studies have found no association between smoking and SARS -CoV-2 antibody concentrations (45,46). The study methodology and demographic characteristics between studies may explain this finding variati ons between studies. 5.1 Conclusion This study has revealed a high prevalence of SARS-CoV-2 IgG antibodies among HCWs in our setting. These

reveal that most HCWs are exposed to SARS-CoV-2 infection and thus probably more seroprotected. 5.2 Study limitations and strengths of the study This study has successfully demonstrated its purpose, but the scope of this study was limited as such, retrospective assessment of self-reported exposures may be subject to recall bias. This study was conducted in one centre, a tertiary hospital where exposure to the SARS-CoV-2 virus cannot be underestimated. Therefore, a caution must be applied in a nationwide result generalization. Notwithstanding these limitations, this is the first study surveying the seroprevalence of SARS-CoV-2 IgG antibodies among healthcare workers in Tanzania. 5.3 Recommendation This research has thrown up many questions in need of further investigation. More broadly, future research should focus in large cohort to determine the long-term implication of SARS- CoV-2 antibodies such as probability of reinfection and the outcome of vaccination uptake among HCWS in our setting. A reasonable approach tackle HCWs disease exposures is to implement strict preventive measures for communicable diseases in society to reduce the burden in hospitals. Financial Disclosure statement; The East African Consortium of Clinical Research (EACCR) under EDTCP funds sponsored this study as a component of the large project "Emerging and Re -emerging Neglected Infectious Disease". Competing interests: None Declared

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