A post-marketing study to evaluate the safety and immunogenicity of a quadrivalent influenza split-virion vaccine in elderly people aged 60 years and older

A post-marketing study to evaluate the safety and immunogenicity of a quadrivalent influenza split-virion vaccine in elderly people aged 60 years and older | 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 A post-marketing study to evaluate the safety and immunogenicity of a quadrivalent influenza split-virion vaccine in elderly people aged 60 years and older Zengqiang Kou, Xiaoyu Li, Ti Liu, Bei Fan, Wenqi An, Wenjue An, and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4020018/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 15 Sep, 2024 Read the published version in Tropical Diseases, Travel Medicine and Vaccines → Version 1 posted 9 You are reading this latest preprint version Abstract Background Influenza remains a global public health concern. Understanding the vaccination-induced response in an aging population, which is susceptible and at high risk, is essential for disease prevention and control. Here, we report findings on the safety and immunogenicity of a quadrivalent influenza split-virion vaccine (15 µg/subtype/0.5 ml/dose) (hereinafter referred to as the “quadrivalent influenza vaccine”) in a population aged ≥60 years. Methods This open-label, pragmatic post-marketing trial enrolled 1399 older adults to receive one dose of an approved commercially available quadrivalent influenza vaccine manufactured by Hualan Biological Bacterin Co., Ltd. (hereinafter referred to as “Hualan Bio”). Participants with contraindications for the vaccine were excluded, while poor health condition was acceptable. All vaccinated subjects experiencedadverse events collection within 30 days and serious adverse events within 180 days post-vaccination. 25% subjects, selected randomly, underwent venous blood sampling pre-vaccination and 30 days afterpost-vaccination, for detecting antibody titers against each subtype of influenza virus by hemagglutination inhibition assay. The incidences of adverse events and antibody titers against each subtype of influenza virus were statistically analyzed using SAS 9.4. Results No grade 3 adverse reactions occurred within 30 days post-vaccination. The incidences of overall adverse reactions, local adverse reactions and systemic adverse reactions were 3.79%, 2.86% and 1.00%, respectively. No serious adverse reactions occurred within 180 days post-vaccination. There were 350 subjects who completed venous blood sampling pre-vaccination, among whom 348 subjects completed venous blood sampling at 30 days post-vaccination for immunogenicity assessment. With respect to hemagglutination inhibition antibodies against influenza viruses H1N1, H3N2, BV and BY subtypes, at 30 days post-vaccination, the seroconversion rates were 87.64%, 75.57%, 73.28% and 78.74%, respectively; the seropositive rates were 93.97%, 98.56%, 79.31% and 95.40%, respectively; and the geometric mean increase (GMI) in post-immunization/pre-immunization antibodies was 24.80, 7.26, 10.39 and 7.39, respectively. Conclusion One 15 µg/subtype dose of the vaccine had agood safety profile and elicited favorable immunogenicity among subjects aged ≥60 years. The results of this study indicate that Hualan Bio quadrivalent influenza vaccine strike balance between safety and immunogenicity, supporting unnecessity to increase dosage or inoculation frequency for further enhancing immunogenicity. Trial registration: Registry: Center for drug evaluation, NMPA ( http://www.chinadrugtrials.org.cn ) Registration number: CTR20220316. Registration title: Phase IV clinical study on safety and efficacy of quadrivalent influenza virus split vaccine in larger scale of population. Quadrivalent influenza split-virion vaccine Elderly people Vaccination Safety Immunogenicity Figures Figure 1 Figure 2 Figure 3 1 Introduction Influenza, commonly referred to as flu or grippe, is an acute respiratory infectious disease caused by the influenza virus. Because of the antigenic nature of the influenza virus, which has highly variable antigens, it is difficult to control seasonal influenza which occurs annually. Currently, vaccination is the most effective means to bolster individual protection against influenza infection, especially for susceptible populations. High-risk populations, such as elderly individuals and chronic-disease patients, are generally susceptible to influenza viruses. Influenza incidence among elderly individuals (7.2%) is higher than that among adults (4.4%) [ 1 ] . Worse still for the elderly, influenza is more likely to lead to a high frequency of hospitalization. From 2010 to 2012, the hospitalization rates of the elderly aged ≥ 65 years for acute respiratory infections were 89/100,000–141/100,000 [ 2 ] . Furthermore, the elderly are prone to face risk of serious complications, severe cases and death when suffering from influenza. The mortality rate is the highest among the elderly population compared to other age brackets [ 3 – 8 ] . Up to now, trivalent and quadrivalent inactivated influenza vaccines have been approved for use in the elderly aged ≥ 60 years in China. Strength and immune procedure of all those products was: 15ug/dose for each subtype of virus, vaccinated with one dose (0.5 ml) prior to or during the influenza season. Compared with trivalent inactivated vaccines, quadrivalent products could offer broader protection, given the virological situation of cocirculating B strains. It is widely believed that vaccination-acquired immunity in elderly individuals might be relatively weak due to the decreasing count and proliferation capability of T lymphocytes, as well as a waning immune system with aging. This could be reflected by the criteria issued by the Center for Biologics Evaluation and Research (CBER) of the Food and Drug Administration (FDA) and that by the European Medicines Evaluation Agency (EMEA) [ 9 , 10 ] , that is, influenza vaccination in adult populations should fulfil: 1) seroconversion rate > 40%; 2) seroprotection rate > 70%. That used in the elderly population should fulfil: 1) seroconversion rate > 30%; 2) seroprotection rate > 60%. In order to overcome the negative effect of a waning immune system on the vaccination-acquired immune response in the elderly population, the FDA-approved influenza vaccine enhances vaccine protection in the elderly by increasing the dosage and/or adding adjuvants [ 11 , 12 ] , such as inactivated vaccines with higher dosage of antigen (60.0 µg of hemagglutinin per strain), adjuvanted vaccines, and recombinant vaccines (45.0 µg of hemagglutinin per strain) [ 13 ] . The Hualan Bio quadrivalent influenza split-virion vaccine was approved in China in 2018. Given the limited sample size of its previous pivotal phase Ⅲ clinical trial and the fact that all the included subjects were healthy, the safety and immunogenicity of products used in the elderly with chronic diseases or in poor health conditions lack pragmatic evidence. Especially for immunogenicity, the necessity of increasing the antigen dosage when used in older recipients to reach a protective immune response is still unclear. The emphasis of this study lies in demonstrating the safety and immunogenicity of the Hualan Bio quadrivalent influenza split-virion vaccine among the elderly population in pragmatic conditions to provide further evidence for influenza prevention and control in the elderly population. 2 Subjects and methods Study design This is an open-label, pragmatic post-marketing study. The objective of this study was to evaluate the safety and immunogenicity of a quadrivalent influenza vaccine, with the safety endpoints of the incidence of adverse events and serious adverse events, with immunogenicity endpoints as seroconversion rate, seroprotection rate, geometric mean titer (GMT) and geometric mean increase (GMI) of HI antibodies 30 days post-immunization. This study was carried out in Shandong Province, China, and conducted by the Shandong Center for Disease Control and Prevention (CDC). Before initiation of the study, the protocol, informed consent form (ICF) and other information provided to recipients had been reviewed and approved by the Preventive Medical Ethical Committee of Shandong CDC (No. 2021-70). Study population This study enrolled 1399 elderly subjects aged ≥ 60 years, without contraindications noted in the package insert of quadrivalent influenza vaccine. No rigorous physical or laboratory tests were conducted during the screening, because subjects in poor health condition were acceptable for this pragmatic study. Study vaccine All screening-eligible subjects received one dose of quadrivalent influenza vaccine at the lateral deltoid muscle of the upper arm. The vaccine used in this study was a commercially available quadrivalent influenza split-virion vaccine produced by Hualan Bio that has been approved in China, that contains no adjuvant and 15 µg hemagglutinin per strain including A/H1N1, A/H3N2, B/Victoria and B/Yamagata. Prefilled syringes with 16 ± 1 mm length needles were used for vaccination, with 2/3 length of the needles injected in the lateral deltoid muscle of the upper arm. Batch No.: 202107B054. Stored and transported in 2 ~ 8℃ condition. Safety assessment All vaccinated subjects were observed on-site for 30 min to assess immediate local and systemic adverse events, after which they were followed for 30 days for adverse event collection by recording on a contact card. Long-term safety observations were conducted within 31–180 days with a combination of methods of active monthly follow-up and self-reporting by subjects to collect serious adverse event (SAE) data. Causality between adverse events and vaccination was analyzed in 5 degrees as: definitely-related, probably-related, possibly-related, likely-unrelated, and definitely-unrelated. Vaccination-related adverse events, including definitely-related, probably-related and possibly-related events, were referred to as adverse reactions. The severity of adverse events was categorized following the Guidelines for the classification of adverse events in clinical trials of preventive vaccines issued by the National Medical Products Administration (NMPA) in 2019 [ 14 ] . The collected adverse events were coded according to the Medical Dictionary for Regulatory Activities (MedDRA) and statistically analyzed for incidence and severity. Immunogenicity assessment 25% subjects, assigned randomly when enrolled, underwent venous blood sampling pre-vaccination and at 30 days after vaccination, to detect antibody titers. Immunogenicity evaluation was based on antibody titers against each subtype of influenza virus by micro-HI assay with serum separated from collected blood samples. When statistically analyzed, seroprotection was defined as an HI antibody titer ≥ 1:40, and seroconversion was defined as an HI antibody titer change to ≥ 1:40 post-vaccination from baseline < 1:10 or a ≥ 4-fold increase in HI antibody titer post-vaccination from baseline ≥ 1:10. When the antibody titer was < 1:10, a ratio of 1:5 was used to calculate the GMT. Referring to the NMPA Technical Guidelines for Clinical Research of Seasonal Influenza Virus Vaccine (Exposure Draft) [ 15 ] , FDA Clinical Data Needed to Support the Licensure of Seasonal Inactivated Influenza Vaccines [ 10 ] , and the EMEA Note for Guidance on Harmonisation of Requirements for Influenza Vaccines [ 9 ] , quadrivalent influenza vaccines could be considered to have favorable immunogenicity among populations aged ≥ 60 years if at 30 days post-vaccination 1) The lower bound of the two-sided 95% confidence interval (CI) for the percentage of subjects achieving seroconversion for HI antibodies should meet or exceed 30%; 2) The lower bound of the two-sided 95% CI for the percentage of subjects achieving an HI antibody titer ≥ 1:40 should meet or exceed 60%; 3) The lower bound of the two-sided 95% CI for GMI > 2.0. Statistical analysis We used SAS 9.4 for the statistical analysis of this study. The incidence of adverse events within 0–30 days post-vaccination, as the primary endpoint, and the incidence of SAEs within 0-180 days post-vaccination, as the secondary endpoint, were statistically described along with their Clopper-Pearson two-sided 95% CIs. For estimation of the primary immunogenicity endpoints, immunity assays and statistics were conducted among 350 subjects who were randomly assigned to an immune subset at the time of enrollment. The seroprotection rate and seroconversion rate were estimated, and the corresponding two-sided 95% CIs were derived from the Clopper-Pearson method. The GMTs and GMIs of the HI antibodies against each type of component (H1N1, H3N2, BV and BY) were calculated together with their two-sided 95% CIs. The safety set (SS) includes data from all vaccinated subjects with at least one safety observation, while data from subjects with protocol violations were not excluded. The full analysis set (FAS) included data from all vaccinated subjects with detectable results from pre- or post-vaccination serum. The per-protocol set (PPS) includes data from subjects who underwent vaccination and blood sampling following predefined protocol requirements, with valid antibody detection results from pre-and post-vaccination serum. Serological methods All the serum samples were treated by the National Institutes for Food and Drug Control in strict accordance with regulations and laboratory manuals. The micro-HI test was used to detect HI antibodies. 3 Results Demographics and Distribution A total of 1399 subjects, all Han Chinese, aged ≥ 60 years, were enrolled in this study and were vaccinated. All vaccinated subjects completed 30 min of on-site observation and were included in the SS analysis set. Among these, 350 subjects completed pre-vaccination blood sampling and were included in the FAS analysis set. After eliminating one subject who dropped out and one subject who reported protocol deviation, 348 subjects completed post-vaccination blood sampling and were included in the PPS analysis set (Fig. 1 ). The ages of all 1399 subjects ranged from 60 years to 96 years, with a median age of 69 years, and the sex distribution of all subjects was 666 males (47.61%) and 733 females (52.39%). Safety Within 0–30 days post-vaccination, the incidences of overall adverse reactions, local adverse reactions and systemic adverse reactions were 3.79%, 2.86%, and 1.00%, respectively (Table 1 ). Table 1 Incidence of Adverse Reactions within 0–30 Days Item N n Incidences (95%CI) Overall ARs 1399 53 3.79(2.85 ~ 4.93) Local ARs 1399 40 2.86(2.05 ~ 3.87) Systemic ARs 1399 14 1.00(0.55 ~ 1.67) AR: adverse reaction; CI: confidence intervals; N: subject number of analyzing set as denominator; n: number of subjects developed corresponding reactions Within 0–30 days post-vaccination, no grade 3 or worse adverse reactions developed. The incidences of Grade 2 and Grade 1 adverse reactions were 0.21% and 3.65%, respectively; the incidences of Grade 2 and Grade 1 local adverse reactions were 0.07% and 2.86%, respectively; and the incidences of Grade 2 and Grade 1 systemic adverse reactions were 0.14% and 0.86%, respectively (Table 2 ). Table 2 Incidence of Adverse Reactions within 0–30 Days by Severity Items N Grade 1 Grade 2 Grade 3 n % (95%CI) n % (95%CI) n % (95%CI) Overall ARs 1399 51 3.65(2.73 ~ 4.77) 3 0.21(0.04 ~ 0.63) 0 0.00(0.00 ~ 0.26) Local ARs 1399 40 2.86(2.05 ~ 3.87) 1 0.07(0.00 ~ 0.40) 0 0.00(0.00 ~ 0.26) Systemic ARs 1399 12 0.86(0.44 ~ 1.49) 2 0.14(0.02 ~ 0.52) 0 0.00(0.00 ~ 0.26) AR: adverse reaction; CI: confidence intervals; N: subject number of analyzing set as denominator; n: number of subjects developed corresponding reactions; %: incidence of subjects developed corresponding reactions. No vaccination-related serious adverse events developed during the whole study period, within 180 days post-vaccination. By coding collected adverse reactions with MedDRA, all reactions could be categorized into 13 preferred terms (PTs). Symptoms developed in elderly subjects after being vaccinated with quadrivalent influenza vaccine included common adverse reactions (1%~10%) , such as vaccination site pain (2.5%); uncommon adverse reactions (0.1%~1%) , such as vaccination site pruritus (0.4%), cough (0.3%), vomiting (0.2%), vaccination site swelling (0.1%), vaccination site erythema (0.1%), headache (0.1%), fatigue (0.1%), and nausea (0.1%); and rare adverse reactions (0.015 ~ 0.1%) , such as pyrexia (0.07%), dizziness (0.07%), arthralgia (0.07%), and myalgia (0.07%) (Table 3 ). Table 3 Incidence of Adverse Reactions within 0–30 Days by Symptoms Symptoms (PT) N n Incidences (95%CI) Vaccination site pain 1399 35 2.50(1.75 ~ 3.46) Vaccination site pruritus 1399 6 0.43(0.16 ~ 0.93) Cough 1399 4 0.29(0.08 ~ 0.73) Vomiting 1399 3 0.21(0.04 ~ 0.63) Vaccination site swelling 1399 2 0.14(0.02 ~ 0.52) Vaccination site erythema 1399 2 0.14(0.02 ~ 0.52) Headache 1399 2 0.14(0.02 ~ 0.52) Fatigue 1399 2 0.14(0.02 ~ 0.52) Nausea 1399 2 0.14(0.02 ~ 0.52) Pyrexia 1399 1 0.07(0.00 ~ 0.40) Dizziness 1399 1 0.07(0.00 ~ 0.40) Arthralgia 1399 1 0.07(0.00 ~ 0.40) Myalgia 1399 1 0.07(0.00 ~ 0.40) PTs in descending order of incidence; CI: confidence intervals; N: subject number of analyzing set as denominator; n: number of subjects developed corresponding reactions Immunogenicity At 30 days post-vaccination, the seroconversion rates (95% CI) of the HI antibody against the H1N1, H3N2, BV and BY subtypes were 87.64% (83.72%~90.91%), 75.57% (70.71%~80.00%), 73.28% (68.30%~77.85%), and 78.74% (74.06%~82.92%), respectively. The lower bounds of the two-sided 95% CIs for the seroconversion rate of each subtype exceeded 40%. The seroprotection rates (95% CIs) of the HI antibody against each subtype were 93.97% (90.92%~96.23%), 98.56% (96.68%~99.53%), 79.31% (74.67%~83.44%), and 95.40% (92.64%~97.35%), respectively (Fig. 2 B). The lower bounds of the two-sided 95% CIs for the seroprotection rate of each subtype all exceeded 70% (Table 4 ). In most subjects, the HI antibody titers against H1N1 (70.69%) and H3N2 (53.16%) exceeded 1:320, those against BY (56.32%) exceeded 1:160, and those against BV (61.21%) exceeded 1:80 (Fig. 3 ). Table 4 Seroconversion and Seroprotection Rate on Day 30 post-vaccination (PPS) Subtype N Seroconversion Seroprotection n % n % H1N1 348 305 87.64(83.72 ~ 90.91) 327 93.97(90.92 ~ 96.23) H3N2 348 263 75.57(70.71 ~ 80.00) 343 98.56(96.68 ~ 99.53) BV 348 255 73.28(68.30 ~ 77.85) 276 79.31(74.67 ~ 83.44) BY 348 274 78.74(74.06 ~ 82.92) 332 95.40(92.64 ~ 97.35) Analyzed with titer detected by hemagglutination inhibition assay. N: subject number of analyzing set as denominator; n: number of subjects whose detection result of corresponding subtype meet seroconversion/seroprotection standard; %: incidences of subjects whose detection result of corresponding subtype meet seroconversion/seroprotection standard. Seroprotection is defined as hemagglutination inhibition (HI) antibody titer ≥ 1:40. Seroconversion is defined as HI titer post-vaccination changed to ≥ 1:40 from baseline < 1:10 or ≥ 4-fold increase in HI titer post-vaccination from baseline ≥ 1:10. At 30 days post-vaccination, the GMTs (95% CI) of the HI antibodies against H1N1, H3N2, BV and BY were 303.29 (267.03 ~ 344.37), 238.98 (212.93 ~ 267.76), 73.16 (64.86 ~ 82.49), and 145.74 (130.65 ~ 162.49), respectively (Fig. 2 A), of which the GMIs (95% CI) were 24.80 (21.39 ~ 28.75), 7.26 (6.38 ~ 8.25), 10.39 (9.14 ~ 11.80), and 7.39 (6.57 ~ 8.31), respectively, of the baseline levels. The lower bounds of the two-sided 95% CIs for the GMI of each subtype all exceeded 2.5 (Table 5 ). Table 5 GMT and GMI on Day 30 post-vaccination (PPS) Subtype N GMT (95%CI) GMI (95%CI) H1N1 348 303.25(267.03 ~ 344.37) 24.80(21.39 ~ 28.75) H3N2 348 238.78(212.93 ~ 267.76) 7.26(6.38 ~ 8.25) BV 348 73.14(64.86 ~ 82.49) 10.39(9.14 ~ 11.80) BY 348 145.70(130.65 ~ 162.49) 7.39(6.57 ~ 8.31) Analyzed with titer detected by hemagglutination inhibition assay. N: subject number of analyzing set as denominator; CI: confidence intervals; GMT: Geometric mean titer; GMI: Geometric mean increase fold at 30 days post-vaccination compared to baseline level. The results of the immunogenicity analysis of the FAS were in accordance with those of the PPS. 4 Discussion This study aimed to provide pragmatic post-marketing evidence of quadrivalent influenza vaccine used in older recipients for health system policy makers to guide the delivery of influenza vaccines in the elderly. By loosening the eligibility criteria, compared to that of previous randomized controlled trials (RCTs), this study enrolled subjects aged ≥ 60 years without contraindications noted in the package insert of quadrivalent influenza vaccines. Elderly individuals with chronic disease or in poor health were accepted to enrolment. This licensed vaccine exhibited a favorable safety profile after inoculation in the target population. Adverse reactions that developed within 30 days post-vaccination were mostly limited to Grade 1, and no Grade 3 or worse adverse reactions developed. The frequency of adverse events was relatively lower than that of the other study conducted in population aged 3–60 years, because elderly people are less sensitive to discomfort [ 16 ] . Compared to clinical trials conducted in China with the other local-unlicensed product, the relatively low incidences of local reactions and systemic reactions could be attributed to the psychological presupposition of subjects for licensed product [ 17 ] . Blood samples from 348 subjects were collected at 30 days post-vaccination for HI assays to evaluate immunogenicity. The lower bounds of the two-sided 95% CIs for seroconversion rates, seroprotection rates, GMTs and GMIs of each subtype all exceed standards issued by the NMPA, FDA and EMEA. Going through the 3-year epidemic of the novel coronavirus, the societal impact and disease burden of respiratory infectious disease on the elderly population have been fully recognized, and people’s attention and awareness of vaccination have greatly improved. It was pointed out in China’s 7th population census that, by the end of 2020, the elderly population aged 60 and above had reached 264 million, accounting for 18.7% of the entire population, which will keep increasing [ 18 ] . The aging of the Chinese population has become a serious social and public health issue concerning the elderly and merits close attention. It is generally believed in developed countries that the immunogenicity elicited by currently licensed influenza split-virion vaccines (15 µg/subtype/0.5 ml/dose) when used in older populations is relatively weak to generate ideal immune protection; thus, influenza vaccines specifically for the elderly use were developed by increasing the dosage or adding adjuvants [ 19 ] . However, this study demonstrated that the Hualan Bio quadrivalent influenza vaccine manifests favorable immunogenicity and safety profiles not only in pivotal phase Ⅲ trial, but also among elderly individuals aged ≥ 60 years in pragmatic conditions, the immunogenicity of which exceeds standards issued by the FDA and EMEA. In addition to product characteristics, influenza epidemiology in China might also be involved. The possibility that older Chinese people have stronger immune memory against influenza virus than people in developed countries cannot be ruled out. In addition, considering that herd protection indirectly protects the unvaccinated population when the coverage of the vaccinated community reaches a certain level, the pragmatic evidence generated in this study is still not sufficiently comprehensive. This may constitute the objective of future studies, and we are arranging further studies evaluating herd protection to provide more well-rounded scientific evidence for influenza prevention and control strategies. 5 Conclusion This study strongly demonstrated that the Hualan Bio quadrivalent influenza vaccine raises no safety concerns and could elicit a protective titer of HI antibodies against vaccine-matched subtypes at 30 days post-vaccination in older adults. The vaccine-acquired immunogenicity profile meets the standards issued by the NMPA, FDA and EMEA, even without increasing the dosage for the elderly specifically. Taken together, the immunogenicity and safety results of this study suggest that the Hualan Bio quadrivalent influenza split-virion vaccine has the potential to further address the disease burden of influenza, especially in elderly people. In addition, it will be worthwhile to conduct additional studies to evaluate herd protection to more fully understand the performance of the vaccine under real-world conditions. Abbreviations CBER: Center for Biologics Evaluation and Research; CDC: Center for Disease Control and Prevention; CI: confidence interval; EMEA: the European Medicines Evaluation Agency; FAS: full analysis set; FDA: Food and Drug Administration; GMI: geometric mean increase; GMT: geometric mean titer; HI: hemagglutination inhibition; ICF: informed consent form; MedDRA: medical dictionary for regulatory activities; NMPA: National Medical Products Administration; PPS: per protocol set; PT: preferred term; RCT: randomized controlled trial; SAE: serious adverse event; SS: safety set. Declarations Ethics approval and consent to participate This trial was conducted at the Shandong CDC and had been approved by the Preventive Medical Ethical Committee of Shandong CDC (reference number 2021-70). Based on regulations by the Declaration of Helsinki, subjects were given detailed information regarding the trial and signed an informed consent form prior to recruitment. Consent for publication All the authors have given their consent for the publication of this article. 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 Ruowen Pan, Wenjue An, Ke Zhang, Jingning Tang and Nan Zhu are employed by Hualan Biological Bacterin Co., Ltd., who funded this research. Bei Fan and Wenqi An are employed by Hualan Biological Engineering Co., Ltd., which is the parent company of Hualan Biological Bacterin Co., Ltd. Zengqiang Kou is employed by the Shandong Center for Disease Control and Prevention and was responsible for the implementation of this research. The other authors report that there are no competing interests to declare. Funding This work was supported by Hualan Biological Bacterin Co., Ltd. Author’s contributions Conception and design of the study: Zengqiang Kou, Ruowen Pan, Xiaoyu Li, Ti Liu, Bei Fan, Wenqi An, Wenjue An, Mingan Dang, Ke Zhang. Acquisition of data: Ti Liu, Nan Zhu. Analysis and interpretation of data: Zengqiang Kou, Ke Zhang, Jingning Tang. Drafting the article: Ke Zhang, Jingning Tang, Nan Zhu, Ti Liu. Critically revising the article: Xiaoyu Li, Bei Fan, Wenqi An, Wenjue An, Mingan Dang, Zengqiang Kou, Ruowen Pan. Final approval of the version to be submitted: Zengqiang Kou, Xiaoyu Li, Ti Liu, Bei Fan, Wenqi An, Wenjue An, Mingan Dang, Ke Zhang, Jingning Tang, Nan Zhu, Ruowen Pan. Project administration: Ti Liu, Nan Zhu . Supervision: Zengqiang Kou, Ruowen Pan . Provide resources: Zengqiang Kou, Wenqi An . Funding: Wenjue An, Bei Fan . Visualization: Xiaoyu Li . Acknowledgments This work was supported by Hualan Biological Bacterin Co., Ltd. All authors critically reviewed the draft and provided valuable feedback on the development of this manuscript. 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Verstraeten, A systematic review and meta-analysis on the safety of newly adjuvanted vaccines among children. Vaccine, 2016. https://doi.org/10.1016/j.vaccine.2015.12.024. Grohskopf, L.A., L.H. Blanton, J.M. Ferdinands, J.R. Chung, K.R. Broder, H.K. Talbot, et al., Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices — United States, 2022–23 Influenza Season. MMWR Recomm Rep, 2022. https://doi.org/10.15585/mmwr.rr7101a1. NMPA. Guidelines for the classification of adverse events in clinical trials of preventive vaccines. 2019. https://www.nmpa.gov.cn/xxgk/ggtg/ypggtg/ypqtggtg/20191231111901460.html. Accessed 04 Mar 2024. NMPA. Technical Guidelines for Clinical Research of Seasonal Influenza Virus Vaccine (Exposure Draft). 2021. https://www.cde.org.cn/main/news/viewInfoCommon/237d5f7de6bcfcd08037dcce873794f3. Accessed 04 Mar 2024. Huang, X., T. Fan, L. Li, X. Nian, J. Zhang, X. Gao, et al., Safety and immunogenicity of a quadrivalent, inactivated, split-virion influenza vaccine (IIV4-W) in healthy people aged 3-60 years: a phase III randomized clinical noninferiority trial. Human Vaccines & Immunotherapeutics, 2022. https://doi.org/10.1080/21645515.2022.2079924. Liu, X., J. Park, S. Xia, B. Liang, S. Yang, Y. Wang, et al., Immunological non-inferiority and safety of a quadrivalent inactivated influenza vaccine versus two trivalent inactivated influenza vaccines in China: Results from two studies. Human Vaccines & Immunotherapeutics, 2022. https://doi.org/10.1080/21645515.2022.2132798. National Bureau of Statistics. State Statistics Bureau Bulletin of the seventh national population Census (No.5). 2021. https://www.stats.gov.cn/sj/tjgb/rkpcgb/qgrkpcgb/202302/t20230206_1902005.html. Accessed 04 Mar 2024. Quach, H.Q. and R.B. Kennedy, Enhancing Immunogenicity of Influenza Vaccine in the Elderly through Intradermal Vaccination: A Literature Analysis. Viruses, 2022. https://doi.org/10.3390/v14112438. Additional Declarations Competing interest reported. R.P., Wenjue A., K.Z., J.T. and N.Z are employed in Hualan Biological Bacterin Co., Ltd. that funded this research. B.F. and Wenqi A. are employed in Hualan Biological Engineering Co., Ltd. that is the parent company of Hualan Biological Bacterin Co., Ltd. Z.K. is employed in Shandong Center for Disease Control and Prevention that was responsible for implement of this research. Other authors report there are no competing interests to declare. Cite Share Download PDF Status: Published Journal Publication published 15 Sep, 2024 Read the published version in Tropical Diseases, Travel Medicine and Vaccines → Version 1 posted Editorial decision: Revision requested 29 May, 2024 Reviews received at journal 24 May, 2024 Reviewers agreed at journal 24 May, 2024 Reviews received at journal 03 May, 2024 Reviewers agreed at journal 27 Apr, 2024 Reviewers invited by journal 07 Apr, 2024 Submission checks completed at journal 01 Apr, 2024 Editor assigned by journal 01 Apr, 2024 First submitted to journal 06 Mar, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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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-4020018","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":281588674,"identity":"18008b1a-d777-49e3-8187-d37510881f04","order_by":0,"name":"Zengqiang Kou","email":"","orcid":"","institution":"Shandong Center for Disease Control and Prevention","correspondingAuthor":false,"prefix":"","firstName":"Zengqiang","middleName":"","lastName":"Kou","suffix":""},{"id":281588675,"identity":"cc36c580-9408-41b7-9a3d-d61edb810bd8","order_by":1,"name":"Xiaoyu Li","email":"","orcid":"","institution":"National Institutes for Food and Drug Control","correspondingAuthor":false,"prefix":"","firstName":"Xiaoyu","middleName":"","lastName":"Li","suffix":""},{"id":281588677,"identity":"85369a88-e050-4e70-953e-613cb2b94259","order_by":2,"name":"Ti Liu","email":"","orcid":"","institution":"Shandong Center for Disease Control and Prevention","correspondingAuthor":false,"prefix":"","firstName":"Ti","middleName":"","lastName":"Liu","suffix":""},{"id":281588679,"identity":"d4e06c99-78ee-4905-8b74-c5d52f322efd","order_by":3,"name":"Bei Fan","email":"","orcid":"","institution":"Hualan Biological Engineering Inc","correspondingAuthor":false,"prefix":"","firstName":"Bei","middleName":"","lastName":"Fan","suffix":""},{"id":281588681,"identity":"2cffab4b-3244-4e6c-979f-459a862e26ec","order_by":4,"name":"Wenqi An","email":"","orcid":"","institution":"Hualan Biological Engineering Inc","correspondingAuthor":false,"prefix":"","firstName":"Wenqi","middleName":"","lastName":"An","suffix":""},{"id":281588683,"identity":"074cb73c-5e93-4e48-9682-ce58c0902e7f","order_by":5,"name":"Wenjue An","email":"","orcid":"","institution":"Hualan Biological Bacterin Co., Ltd","correspondingAuthor":false,"prefix":"","firstName":"Wenjue","middleName":"","lastName":"An","suffix":""},{"id":281588686,"identity":"c76cdad0-7eec-4ff6-aeaf-20fd1294c4bc","order_by":6,"name":"Mingan Dang","email":"","orcid":"","institution":"Henan Center for Drug Evaluation and Inspection","correspondingAuthor":false,"prefix":"","firstName":"Mingan","middleName":"","lastName":"Dang","suffix":""},{"id":281588688,"identity":"5628d9c3-0c6f-4b07-a34a-70bcf9e955e4","order_by":7,"name":"Ke Zhang","email":"","orcid":"","institution":"Hualan Biological Bacterin Co., Ltd","correspondingAuthor":false,"prefix":"","firstName":"Ke","middleName":"","lastName":"Zhang","suffix":""},{"id":281588692,"identity":"5dd88c05-2565-46fd-b3e9-bd1dadfe6933","order_by":8,"name":"Jingning Tang","email":"","orcid":"","institution":"Hualan Biological Bacterin Co., Ltd","correspondingAuthor":false,"prefix":"","firstName":"Jingning","middleName":"","lastName":"Tang","suffix":""},{"id":281588696,"identity":"b055bd84-4d3c-4661-93d0-3ba20ae0c9e9","order_by":9,"name":"Nan Zhu","email":"","orcid":"","institution":"Hualan Biological Bacterin Co., Ltd","correspondingAuthor":false,"prefix":"","firstName":"Nan","middleName":"","lastName":"Zhu","suffix":""},{"id":281588697,"identity":"e26dadfa-d5eb-4eb4-af50-ba9059d0e5c3","order_by":10,"name":"Ruowen Pan","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA2klEQVRIiWNgGAWjYBACA3Yg8cFAop4fxHsAFCCshZmBgXFGhU2CZAMDY0MCsVqYec6kJRgcIFaLOTOP6QbetsN5xsd7zB8kVNgYM7AfProBnxbLZh6zG5Jth4vNzpwxbEg4k2bGwJOWdgOvww4DtRi2HWbcdiPHsCGx7bANgwRQhKAWoErGzTNI0nLgTFriBgmIFjMitLCV3WwA+lrizLHCGUC/GLMR9Mvx5m23/xhIyPG3N2/48KHCxrCf/fAxvFoYGDjQYoINv3IQYH9AWM0oGAWjYBSMbAAAKodP731wDhgAAAAASUVORK5CYII=","orcid":"","institution":"Hualan Biological Bacterin Co., Ltd","correspondingAuthor":true,"prefix":"","firstName":"Ruowen","middleName":"","lastName":"Pan","suffix":""}],"badges":[],"createdAt":"2024-03-06 08:31:02","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4020018/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4020018/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s40794-024-00228-x","type":"published","date":"2024-09-15T15:58:13+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":53191264,"identity":"1ea557fd-37fa-4bbe-bd03-aac06843a487","added_by":"auto","created_at":"2024-03-21 17:35:55","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":206925,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eAnalysis Set Distribution of the Subjects\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-4020018/v1/ccf3fd070edf302199417764.png"},{"id":53191261,"identity":"f496a2c2-a76a-46fe-a604-2ca5f1adeb2e","added_by":"auto","created_at":"2024-03-21 17:35:55","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":25634,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eGMT and Seroprotection Rate of Hemagglutination Inhibition (HI) Antibodies\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u003cstrong\u003eLegend: \u003c/strong\u003e\u003c/em\u003e\u003cem\u003eData was analyzed among 348 subjects included in PPS.\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u003cstrong\u003eA:\u003c/strong\u003e\u003c/em\u003e\u003cem\u003e GMT of HI antibody at baseline and 30 days post-vaccination; \u003c/em\u003e\u003cem\u003e\u003cstrong\u003eB: \u003c/strong\u003e\u003c/em\u003e\u003cem\u003eSeroprotection Rate of HI antibody at baseline and 30 days post-vaccination.\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eSeroprotection was defined as an antibody titer ≥1:40\u003c/em\u003e\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-4020018/v1/74ed537858b379d2ef8390fa.png"},{"id":53191260,"identity":"ba50d868-0be6-4ec7-ab6c-f1af6d573d7d","added_by":"auto","created_at":"2024-03-21 17:35:55","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":139547,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eReverse Cumulative Distribution Curve for Antibody Titer\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-4020018/v1/441762f549c62f7924e8ccef.png"},{"id":64620115,"identity":"d20f87b9-7070-4ae4-be4e-a5e07184af38","added_by":"auto","created_at":"2024-09-16 16:17:55","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1071412,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4020018/v1/df71c28a-c638-4240-81d0-d2dfca48cf68.pdf"}],"financialInterests":"Competing interest reported. R.P., Wenjue A., K.Z., J.T. and N.Z are employed in Hualan Biological Bacterin Co., Ltd. that funded this research. B.F. and Wenqi A. are employed in Hualan Biological Engineering Co., Ltd. that is the parent company of Hualan Biological Bacterin Co., Ltd. Z.K. is employed in Shandong Center for Disease Control and Prevention that was responsible for implement of this research. Other authors report there are no competing interests to declare.","formattedTitle":"A post-marketing study to evaluate the safety and immunogenicity of a quadrivalent influenza split-virion vaccine in elderly people aged 60 years and older","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eInfluenza, commonly referred to as flu or grippe, is an acute respiratory infectious disease caused by the influenza virus. Because of the antigenic nature of the influenza virus, which has highly variable antigens, it is difficult to control seasonal influenza which occurs annually. Currently, vaccination is the most effective means to bolster individual protection against influenza infection, especially for susceptible populations. High-risk populations, such as elderly individuals and chronic-disease patients, are generally susceptible to influenza viruses. Influenza incidence among elderly individuals (7.2%) is higher than that among adults (4.4%)\u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]\u003c/sup\u003e. Worse still for the elderly, influenza is more likely to lead to a high frequency of hospitalization. From 2010 to 2012, the hospitalization rates of the elderly aged\u0026thinsp;\u0026ge;\u0026thinsp;65 years for acute respiratory infections were 89/100,000\u0026ndash;141/100,000\u003csup\u003e[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/sup\u003e. Furthermore, the elderly are prone to face risk of serious complications, severe cases and death when suffering from influenza. The mortality rate is the highest among the elderly population compared to other age brackets\u003csup\u003e[\u003cspan additionalcitationids=\"CR4 CR5 CR6 CR7\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eUp to now, trivalent and quadrivalent inactivated influenza vaccines have been approved for use in the elderly aged\u0026thinsp;\u0026ge;\u0026thinsp;60 years in China. Strength and immune procedure of all those products was: 15ug/dose for each subtype of virus, vaccinated with one dose (0.5 ml) prior to or during the influenza season. Compared with trivalent inactivated vaccines, quadrivalent products could offer broader protection, given the virological situation of cocirculating B strains. It is widely believed that vaccination-acquired immunity in elderly individuals might be relatively weak due to the decreasing count and proliferation capability of T lymphocytes, as well as a waning immune system with aging. This could be reflected by the criteria issued by the Center for Biologics Evaluation and Research (CBER) of the Food and Drug Administration (FDA) and that by the European Medicines Evaluation Agency (EMEA)\u003csup\u003e[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/sup\u003e, that is, influenza vaccination in adult populations should fulfil: 1) seroconversion rate\u0026thinsp;\u0026gt;\u0026thinsp;40%; 2) seroprotection rate\u0026thinsp;\u0026gt;\u0026thinsp;70%. That used in the elderly population should fulfil: 1) seroconversion rate\u0026thinsp;\u0026gt;\u0026thinsp;30%; 2) seroprotection rate\u0026thinsp;\u0026gt;\u0026thinsp;60%. In order to overcome the negative effect of a waning immune system on the vaccination-acquired immune response in the elderly population, the FDA-approved influenza vaccine enhances vaccine protection in the elderly by increasing the dosage and/or adding adjuvants\u003csup\u003e[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]\u003c/sup\u003e, such as inactivated vaccines with higher dosage of antigen (60.0 \u0026micro;g of hemagglutinin per strain), adjuvanted vaccines, and recombinant vaccines (45.0 \u0026micro;g of hemagglutinin per strain)\u003csup\u003e[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e The Hualan Bio quadrivalent influenza split-virion vaccine was approved in China in 2018. Given the limited sample size of its previous pivotal phase Ⅲ clinical trial and the fact that all the included subjects were healthy, the safety and immunogenicity of products used in the elderly with chronic diseases or in poor health conditions lack pragmatic evidence. Especially for immunogenicity, the necessity of increasing the antigen dosage when used in older recipients to reach a protective immune response is still unclear. The emphasis of this study lies in demonstrating the safety and immunogenicity of the Hualan Bio quadrivalent influenza split-virion vaccine among the elderly population in pragmatic conditions to provide further evidence for influenza prevention and control in the elderly population.\u003c/p\u003e"},{"header":"2 Subjects and methods","content":"\u003cp\u003e \u003cb\u003eStudy design\u003c/b\u003e \u003c/p\u003e \u003cp\u003eThis is an open-label, pragmatic post-marketing study. The objective of this study was to evaluate the safety and immunogenicity of a quadrivalent influenza vaccine, with the safety endpoints of the incidence of adverse events and serious adverse events, with immunogenicity endpoints as seroconversion rate, seroprotection rate, geometric mean titer (GMT) and geometric mean increase (GMI) of HI antibodies 30 days post-immunization.\u003c/p\u003e \u003cp\u003eThis study was carried out in Shandong Province, China, and conducted by the Shandong Center for Disease Control and Prevention (CDC). Before initiation of the study, the protocol, informed consent form (ICF) and other information provided to recipients had been reviewed and approved by the Preventive Medical Ethical Committee of Shandong CDC (No. 2021-70).\u003c/p\u003e \u003cp\u003e \u003cb\u003eStudy population\u003c/b\u003e \u003c/p\u003e \u003cp\u003eThis study enrolled 1399 elderly subjects aged\u0026thinsp;\u0026ge;\u0026thinsp;60 years, without contraindications noted in the package insert of quadrivalent influenza vaccine. No rigorous physical or laboratory tests were conducted during the screening, because subjects in poor health condition were acceptable for this pragmatic study.\u003c/p\u003e \u003cp\u003e \u003cb\u003eStudy vaccine\u003c/b\u003e \u003c/p\u003e \u003cp\u003eAll screening-eligible subjects received one dose of quadrivalent influenza vaccine at the lateral deltoid muscle of the upper arm. The vaccine used in this study was a commercially available quadrivalent influenza split-virion vaccine produced by Hualan Bio that has been approved in China, that contains no adjuvant and 15 \u0026micro;g hemagglutinin per strain including A/H1N1, A/H3N2, B/Victoria and B/Yamagata. Prefilled syringes with 16\u0026thinsp;\u0026plusmn;\u0026thinsp;1 mm length needles were used for vaccination, with 2/3 length of the needles injected in the lateral deltoid muscle of the upper arm. Batch No.: 202107B054. Stored and transported in 2\u0026thinsp;~\u0026thinsp;8℃ condition.\u003c/p\u003e \u003cp\u003e \u003cb\u003eSafety assessment\u003c/b\u003e \u003c/p\u003e \u003cp\u003eAll vaccinated subjects were observed on-site for 30 min to assess immediate local and systemic adverse events, after which they were followed for 30 days for adverse event collection by recording on a contact card. Long-term safety observations were conducted within 31\u0026ndash;180 days with a combination of methods of active monthly follow-up and self-reporting by subjects to collect serious adverse event (SAE) data.\u003c/p\u003e \u003cp\u003eCausality between adverse events and vaccination was analyzed in 5 degrees as: definitely-related, probably-related, possibly-related, likely-unrelated, and definitely-unrelated. Vaccination-related adverse events, including definitely-related, probably-related and possibly-related events, were referred to as adverse reactions. The severity of adverse events was categorized following the \u003cem\u003eGuidelines for the classification of adverse events in clinical trials of preventive vaccines\u003c/em\u003e issued by the National Medical Products Administration (NMPA) in 2019\u003csup\u003e[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]\u003c/sup\u003e. The collected adverse events were coded according to the Medical Dictionary for Regulatory Activities (MedDRA) and statistically analyzed for incidence and severity.\u003c/p\u003e \u003cp\u003e \u003cb\u003eImmunogenicity assessment\u003c/b\u003e \u003c/p\u003e \u003cp\u003e25% subjects, assigned randomly when enrolled, underwent venous blood sampling pre-vaccination and at 30 days after vaccination, to detect antibody titers. Immunogenicity evaluation was based on antibody titers against each subtype of influenza virus by micro-HI assay with serum separated from collected blood samples.\u003c/p\u003e \u003cp\u003eWhen statistically analyzed, seroprotection was defined as an HI antibody titer\u0026thinsp;\u0026ge;\u0026thinsp;1:40, and seroconversion was defined as an HI antibody titer change to \u0026ge;\u0026thinsp;1:40 post-vaccination from baseline\u0026thinsp;\u0026lt;\u0026thinsp;1:10 or a\u0026thinsp;\u0026ge;\u0026thinsp;4-fold increase in HI antibody titer post-vaccination from baseline\u0026thinsp;\u0026ge;\u0026thinsp;1:10. When the antibody titer was \u0026lt;\u0026thinsp;1:10, a ratio of 1:5 was used to calculate the GMT.\u003c/p\u003e \u003cp\u003eReferring to the NMPA \u003cem\u003eTechnical Guidelines for Clinical Research of Seasonal Influenza Virus Vaccine\u003c/em\u003e (Exposure Draft)\u003csup\u003e[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/sup\u003e, FDA \u003cem\u003eClinical Data Needed to Support the Licensure of Seasonal Inactivated Influenza Vaccines\u003c/em\u003e\u003csup\u003e[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/sup\u003e, and the EMEA \u003cem\u003eNote for Guidance on Harmonisation of Requirements for Influenza Vaccines\u003c/em\u003e\u003csup\u003e[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/sup\u003e, quadrivalent influenza vaccines could be considered to have favorable immunogenicity among populations aged\u0026thinsp;\u0026ge;\u0026thinsp;60 years if at 30 days post-vaccination 1) The lower bound of the two-sided 95% confidence interval (CI) for the percentage of subjects achieving seroconversion for HI antibodies should meet or exceed 30%; 2) The lower bound of the two-sided 95% CI for the percentage of subjects achieving an HI antibody titer\u0026thinsp;\u0026ge;\u0026thinsp;1:40 should meet or exceed 60%; 3) The lower bound of the two-sided 95% CI for GMI\u0026thinsp;\u0026gt;\u0026thinsp;2.0.\u003c/p\u003e \u003cp\u003e \u003cb\u003eStatistical analysis\u003c/b\u003e \u003c/p\u003e \u003cp\u003eWe used SAS 9.4 for the statistical analysis of this study. The incidence of adverse events within 0\u0026ndash;30 days post-vaccination, as the primary endpoint, and the incidence of SAEs within 0-180 days post-vaccination, as the secondary endpoint, were statistically described along with their Clopper-Pearson two-sided 95% CIs. For estimation of the primary immunogenicity endpoints, immunity assays and statistics were conducted among 350 subjects who were randomly assigned to an immune subset at the time of enrollment. The seroprotection rate and seroconversion rate were estimated, and the corresponding two-sided 95% CIs were derived from the Clopper-Pearson method. The GMTs and GMIs of the HI antibodies against each type of component (H1N1, H3N2, BV and BY) were calculated together with their two-sided 95% CIs.\u003c/p\u003e \u003cp\u003eThe safety set (SS) includes data from all vaccinated subjects with at least one safety observation, while data from subjects with protocol violations were not excluded. The full analysis set (FAS) included data from all vaccinated subjects with detectable results from pre- or post-vaccination serum. The per-protocol set (PPS) includes data from subjects who underwent vaccination and blood sampling following predefined protocol requirements, with valid antibody detection results from pre-and post-vaccination serum.\u003c/p\u003e \u003cp\u003e \u003cb\u003eSerological methods\u003c/b\u003e \u003c/p\u003e \u003cp\u003eAll the serum samples were treated by the National Institutes for Food and Drug Control in strict accordance with regulations and laboratory manuals. The micro-HI test was used to detect HI antibodies.\u003c/p\u003e"},{"header":"3 Results","content":"\u003cp\u003e\u003cstrong\u003eDemographics and Distribution\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA total of 1399 subjects, all Han Chinese, aged\u0026thinsp;\u0026ge;\u0026thinsp;60 years, were enrolled in this study and were vaccinated. All vaccinated subjects completed 30 min of on-site observation and were included in the SS analysis set. Among these, 350 subjects completed pre-vaccination blood sampling and were included in the FAS analysis set. After eliminating one subject who dropped out and one subject who reported protocol deviation, 348 subjects completed post-vaccination blood sampling and were included in the PPS analysis set (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e). The ages of all 1399 subjects ranged from 60 years to 96 years, with a median age of 69 years, and the sex distribution of all subjects was 666 males (47.61%) and 733 females (52.39%).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSafety\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWithin 0\u0026ndash;30 days post-vaccination, the incidences of overall adverse reactions, local adverse reactions and systemic adverse reactions were 3.79%, 2.86%, and 1.00%, respectively (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab1\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eIncidence of Adverse Reactions within 0\u0026ndash;30 Days\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eItem\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eN\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003en\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eIncidences (95%CI)\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eOverall ARs\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1399\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e53\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3.79(2.85\u0026thinsp;~\u0026thinsp;4.93)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eLocal ARs\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1399\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e40\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2.86(2.05\u0026thinsp;~\u0026thinsp;3.87)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eSystemic ARs\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1399\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e14\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.00(0.55\u0026thinsp;~\u0026thinsp;1.67)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"4\" align=\"left\"\u003e\n\u003cp\u003eAR: adverse reaction; CI: confidence intervals;\u003c/p\u003e\n\u003cp\u003eN: subject number of analyzing set as denominator; n: number of subjects developed corresponding reactions\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eWithin 0\u0026ndash;30 days post-vaccination, no grade 3 or worse adverse reactions developed. The incidences of Grade 2 and Grade 1 adverse reactions were 0.21% and 3.65%, respectively; the incidences of Grade 2 and Grade 1 local adverse reactions were 0.07% and 2.86%, respectively; and the incidences of Grade 2 and Grade 1 systemic adverse reactions were 0.14% and 0.86%, respectively (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab2\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eIncidence of Adverse Reactions within 0\u0026ndash;30 Days by Severity\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth rowspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eItems\u003c/p\u003e\n\u003c/th\u003e\n\u003cth rowspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eN\u003c/p\u003e\n\u003c/th\u003e\n\u003cth colspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eGrade 1\u003c/p\u003e\n\u003c/th\u003e\n\u003cth colspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eGrade 2\u003c/p\u003e\n\u003c/th\u003e\n\u003cth colspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eGrade 3\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003en\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e% (95%CI)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003en\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e% (95%CI)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003en\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e% (95%CI)\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eOverall ARs\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1399\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e51\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3.65(2.73\u0026thinsp;~\u0026thinsp;4.77)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.21(0.04\u0026thinsp;~\u0026thinsp;0.63)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.00(0.00\u0026thinsp;~\u0026thinsp;0.26)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eLocal ARs\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1399\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e40\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2.86(2.05\u0026thinsp;~\u0026thinsp;3.87)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.07(0.00\u0026thinsp;~\u0026thinsp;0.40)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.00(0.00\u0026thinsp;~\u0026thinsp;0.26)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eSystemic ARs\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1399\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e12\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.86(0.44\u0026thinsp;~\u0026thinsp;1.49)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.14(0.02\u0026thinsp;~\u0026thinsp;0.52)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.00(0.00\u0026thinsp;~\u0026thinsp;0.26)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"8\" align=\"left\"\u003e\n\u003cp\u003eAR: adverse reaction; CI: confidence intervals; N: subject number of analyzing set as denominator;\u003c/p\u003e\n\u003cp\u003en: number of subjects developed corresponding reactions; %: incidence of subjects developed corresponding reactions.\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eNo vaccination-related serious adverse events developed during the whole study period, within 180 days post-vaccination.\u003c/p\u003e\n\u003cp\u003eBy coding collected adverse reactions with MedDRA, all reactions could be categorized into 13 preferred terms (PTs). Symptoms developed in elderly subjects after being vaccinated with quadrivalent influenza vaccine included \u003cstrong\u003ecommon adverse reactions (1%~10%)\u003c/strong\u003e, such as vaccination site pain (2.5%); \u003cstrong\u003euncommon adverse reactions (0.1%~1%)\u003c/strong\u003e, such as vaccination site pruritus (0.4%), cough (0.3%), vomiting (0.2%), vaccination site swelling (0.1%), vaccination site erythema (0.1%), headache (0.1%), fatigue (0.1%), and nausea (0.1%); \u003cstrong\u003eand rare adverse reactions (0.015\u0026thinsp;~\u0026thinsp;0.1%)\u003c/strong\u003e, such as pyrexia (0.07%), dizziness (0.07%), arthralgia (0.07%), and myalgia (0.07%) (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab3\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eIncidence of Adverse Reactions within 0\u0026ndash;30 Days by Symptoms\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eSymptoms (PT)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eN\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003en\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eIncidences (95%CI)\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eVaccination site pain\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1399\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e35\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2.50(1.75\u0026thinsp;~\u0026thinsp;3.46)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eVaccination site pruritus\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1399\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e6\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.43(0.16\u0026thinsp;~\u0026thinsp;0.93)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eCough\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1399\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.29(0.08\u0026thinsp;~\u0026thinsp;0.73)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eVomiting\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1399\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.21(0.04\u0026thinsp;~\u0026thinsp;0.63)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eVaccination site swelling\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1399\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.14(0.02\u0026thinsp;~\u0026thinsp;0.52)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eVaccination site erythema\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1399\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.14(0.02\u0026thinsp;~\u0026thinsp;0.52)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eHeadache\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1399\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.14(0.02\u0026thinsp;~\u0026thinsp;0.52)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eFatigue\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1399\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.14(0.02\u0026thinsp;~\u0026thinsp;0.52)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eNausea\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1399\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.14(0.02\u0026thinsp;~\u0026thinsp;0.52)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003ePyrexia\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1399\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.07(0.00\u0026thinsp;~\u0026thinsp;0.40)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eDizziness\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1399\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.07(0.00\u0026thinsp;~\u0026thinsp;0.40)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eArthralgia\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1399\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.07(0.00\u0026thinsp;~\u0026thinsp;0.40)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eMyalgia\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1399\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.07(0.00\u0026thinsp;~\u0026thinsp;0.40)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"4\" align=\"left\"\u003e\n\u003cp\u003ePTs in descending order of incidence;\u003c/p\u003e\n\u003cp\u003eCI: confidence intervals;\u003c/p\u003e\n\u003cp\u003eN: subject number of analyzing set as denominator; n: number of subjects developed corresponding reactions\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003eImmunogenicity\u003c/strong\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cp\u003eAt 30 days post-vaccination, the seroconversion rates (95% CI) of the HI antibody against the H1N1, H3N2, BV and BY subtypes were 87.64% (83.72%~90.91%), 75.57% (70.71%~80.00%), 73.28% (68.30%~77.85%), and 78.74% (74.06%~82.92%), respectively. The lower bounds of the two-sided 95% CIs for the seroconversion rate of each subtype exceeded 40%. The seroprotection rates (95% CIs) of the HI antibody against each subtype were 93.97% (90.92%~96.23%), 98.56% (96.68%~99.53%), 79.31% (74.67%~83.44%), and 95.40% (92.64%~97.35%), respectively (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eB). The lower bounds of the two-sided 95% CIs for the seroprotection rate of each subtype all exceeded 70% (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e). In most subjects, the HI antibody titers against H1N1 (70.69%) and H3N2 (53.16%) exceeded 1:320, those against BY (56.32%) exceeded 1:160, and those against BV (61.21%) exceeded 1:80 (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab4\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eSeroconversion and Seroprotection Rate on Day 30 post-vaccination (PPS)\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth rowspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eSubtype\u003c/p\u003e\n\u003c/th\u003e\n\u003cth rowspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eN\u003c/p\u003e\n\u003c/th\u003e\n\u003cth colspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eSeroconversion\u003c/p\u003e\n\u003c/th\u003e\n\u003cth colspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eSeroprotection\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003en\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e%\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003en\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e%\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eH1N1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e348\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e305\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e87.64(83.72\u0026thinsp;~\u0026thinsp;90.91)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e327\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e93.97(90.92\u0026thinsp;~\u0026thinsp;96.23)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eH3N2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e348\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e263\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e75.57(70.71\u0026thinsp;~\u0026thinsp;80.00)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e343\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e98.56(96.68\u0026thinsp;~\u0026thinsp;99.53)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eBV\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e348\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e255\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e73.28(68.30\u0026thinsp;~\u0026thinsp;77.85)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e276\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e79.31(74.67\u0026thinsp;~\u0026thinsp;83.44)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eBY\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e348\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e274\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e78.74(74.06\u0026thinsp;~\u0026thinsp;82.92)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e332\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e95.40(92.64\u0026thinsp;~\u0026thinsp;97.35)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"6\" align=\"left\"\u003e\n\u003cp\u003eAnalyzed with titer detected by hemagglutination inhibition assay.\u003c/p\u003e\n\u003cp\u003eN: subject number of analyzing set as denominator;\u003c/p\u003e\n\u003cp\u003en: number of subjects whose detection result of corresponding subtype meet seroconversion/seroprotection standard;\u003c/p\u003e\n\u003cp\u003e%: incidences of subjects whose detection result of corresponding subtype meet seroconversion/seroprotection standard.\u003c/p\u003e\n\u003cp\u003eSeroprotection is defined as hemagglutination inhibition (HI) antibody titer\u0026thinsp;\u0026ge;\u0026thinsp;1:40.\u003c/p\u003e\n\u003cp\u003eSeroconversion is defined as HI titer post-vaccination changed to \u0026ge;\u0026thinsp;1:40 from baseline\u0026thinsp;\u0026lt;\u0026thinsp;1:10 or \u0026ge;\u0026thinsp;4-fold increase in HI titer post-vaccination from baseline\u0026thinsp;\u0026ge;\u0026thinsp;1:10.\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eAt 30 days post-vaccination, the GMTs (95% CI) of the HI antibodies against H1N1, H3N2, BV and BY were 303.29 (267.03\u0026thinsp;~\u0026thinsp;344.37), 238.98 (212.93\u0026thinsp;~\u0026thinsp;267.76), 73.16 (64.86\u0026thinsp;~\u0026thinsp;82.49), and 145.74 (130.65\u0026thinsp;~\u0026thinsp;162.49), respectively (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eA), of which the GMIs (95% CI) were 24.80 (21.39\u0026thinsp;~\u0026thinsp;28.75), 7.26 (6.38\u0026thinsp;~\u0026thinsp;8.25), 10.39 (9.14\u0026thinsp;~\u0026thinsp;11.80), and 7.39 (6.57\u0026thinsp;~\u0026thinsp;8.31), respectively, of the baseline levels. The lower bounds of the two-sided 95% CIs for the GMI of each subtype all exceeded 2.5 (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab5\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eGMT and GMI on Day 30 post-vaccination (PPS)\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eSubtype\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eN\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eGMT (95%CI)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eGMI (95%CI)\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eH1N1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e348\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e303.25(267.03\u0026thinsp;~\u0026thinsp;344.37)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e24.80(21.39\u0026thinsp;~\u0026thinsp;28.75)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eH3N2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e348\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e238.78(212.93\u0026thinsp;~\u0026thinsp;267.76)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e7.26(6.38\u0026thinsp;~\u0026thinsp;8.25)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eBV\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e348\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e73.14(64.86\u0026thinsp;~\u0026thinsp;82.49)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e10.39(9.14\u0026thinsp;~\u0026thinsp;11.80)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eBY\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e348\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e145.70(130.65\u0026thinsp;~\u0026thinsp;162.49)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e7.39(6.57\u0026thinsp;~\u0026thinsp;8.31)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"4\" align=\"left\"\u003e\n\u003cp\u003eAnalyzed with titer detected by hemagglutination inhibition assay.\u003c/p\u003e\n\u003cp\u003eN: subject number of analyzing set as denominator; CI: confidence intervals;\u003c/p\u003e\n\u003cp\u003eGMT: Geometric mean titer; GMI: Geometric mean increase fold at 30 days post-vaccination compared to baseline level.\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eThe results of the immunogenicity analysis of the FAS were in accordance with those of the PPS.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"4 Discussion","content":"\u003cp\u003eThis study aimed to provide pragmatic post-marketing evidence of quadrivalent influenza vaccine used in older recipients for health system policy makers to guide the delivery of influenza vaccines in the elderly. By loosening the eligibility criteria, compared to that of previous randomized controlled trials (RCTs), this study enrolled subjects aged\u0026thinsp;\u0026ge;\u0026thinsp;60 years without contraindications noted in the package insert of quadrivalent influenza vaccines. Elderly individuals with chronic disease or in poor health were accepted to enrolment. This licensed vaccine exhibited a favorable safety profile after inoculation in the target population. Adverse reactions that developed within 30 days post-vaccination were mostly limited to Grade 1, and no Grade 3 or worse adverse reactions developed. The frequency of adverse events was relatively lower than that of the other study conducted in population aged 3\u0026ndash;60 years, because elderly people are less sensitive to discomfort\u003csup\u003e[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e. Compared to clinical trials conducted in China with the other local-unlicensed product, the relatively low incidences of local reactions and systemic reactions could be attributed to the psychological presupposition of subjects for licensed product\u003csup\u003e[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]\u003c/sup\u003e. Blood samples from 348 subjects were collected at 30 days post-vaccination for HI assays to evaluate immunogenicity. The lower bounds of the two-sided 95% CIs for seroconversion rates, seroprotection rates, GMTs and GMIs of each subtype all exceed standards issued by the NMPA, FDA and EMEA.\u003c/p\u003e \u003cp\u003eGoing through the 3-year epidemic of the novel coronavirus, the societal impact and disease burden of respiratory infectious disease on the elderly population have been fully recognized, and people\u0026rsquo;s attention and awareness of vaccination have greatly improved. It was pointed out in China\u0026rsquo;s 7th population census that, by the end of 2020, the elderly population aged 60 and above had reached 264\u0026nbsp;million, accounting for 18.7% of the entire population, which will keep increasing\u003csup\u003e[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]\u003c/sup\u003e. The aging of the Chinese population has become a serious social and public health issue concerning the elderly and merits close attention.\u003c/p\u003e \u003cp\u003eIt is generally believed in developed countries that the immunogenicity elicited by currently licensed influenza split-virion vaccines (15 \u0026micro;g/subtype/0.5 ml/dose) when used in older populations is relatively weak to generate ideal immune protection; thus, influenza vaccines specifically for the elderly use were developed by increasing the dosage or adding adjuvants\u003csup\u003e[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]\u003c/sup\u003e. However, this study demonstrated that the Hualan Bio quadrivalent influenza vaccine manifests favorable immunogenicity and safety profiles not only in pivotal phase Ⅲ trial, but also among elderly individuals aged\u0026thinsp;\u0026ge;\u0026thinsp;60 years in pragmatic conditions, the immunogenicity of which exceeds standards issued by the FDA and EMEA. In addition to product characteristics, influenza epidemiology in China might also be involved. The possibility that older Chinese people have stronger immune memory against influenza virus than people in developed countries cannot be ruled out.\u003c/p\u003e \u003cp\u003eIn addition, considering that herd protection indirectly protects the unvaccinated population when the coverage of the vaccinated community reaches a certain level, the pragmatic evidence generated in this study is still not sufficiently comprehensive. This may constitute the objective of future studies, and we are arranging further studies evaluating herd protection to provide more well-rounded scientific evidence for influenza prevention and control strategies.\u003c/p\u003e"},{"header":"5 Conclusion","content":"\u003cp\u003eThis study strongly demonstrated that the Hualan Bio quadrivalent influenza vaccine raises no safety concerns and could elicit a protective titer of HI antibodies against vaccine-matched subtypes at 30 days post-vaccination in older adults. The vaccine-acquired immunogenicity profile meets the standards issued by the NMPA, FDA and EMEA, even without increasing the dosage for the elderly specifically. Taken together, the immunogenicity and safety results of this study suggest that the Hualan Bio quadrivalent influenza split-virion vaccine has the potential to further address the disease burden of influenza, especially in elderly people. In addition, it will be worthwhile to conduct additional studies to evaluate herd protection to more fully understand the performance of the vaccine under real-world conditions.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eCBER: Center for Biologics Evaluation and Research; CDC: Center for Disease Control and Prevention; CI: confidence interval; EMEA: the European Medicines Evaluation Agency; FAS: full analysis set; FDA: Food and Drug Administration; GMI: geometric mean increase; GMT: geometric mean titer; HI: hemagglutination inhibition; ICF: informed consent form; MedDRA: medical dictionary for regulatory activities; NMPA: National Medical Products Administration; PPS: per protocol set; PT: preferred term; RCT: randomized controlled trial; SAE: serious adverse event; SS: safety set.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis trial was conducted at the Shandong CDC and had been approved by the Preventive Medical Ethical Committee of Shandong CDC (reference number 2021-70). Based on regulations by the Declaration of Helsinki, subjects were given detailed information regarding the trial and signed an informed consent form prior to recruitment.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll the authors have given their consent for the publication of this article.\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\u003eRuowen Pan, Wenjue An, Ke Zhang, Jingning Tang and Nan Zhu are employed by Hualan Biological Bacterin Co., Ltd., who funded this research. Bei Fan and Wenqi An are employed by Hualan Biological Engineering Co., Ltd., which is the parent company of Hualan Biological Bacterin Co., Ltd. Zengqiang Kou is employed by the Shandong Center for Disease Control and Prevention and was responsible for the implementation of this research. The other authors report that there are no competing interests to declare.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by Hualan Biological Bacterin Co., Ltd.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor\u0026rsquo;s contributions\u003c/strong\u003e\u003c/p\u003e\n\u003col\u003e\n\u003cli\u003e\n\u003cp\u003eConception and design of the study: \u003cem\u003eZengqiang Kou, Ruowen Pan, Xiaoyu Li, Ti Liu, Bei Fan, Wenqi An, Wenjue An, Mingan Dang, Ke Zhang.\u003c/em\u003e\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eAcquisition of data: \u003cem\u003eTi Liu, Nan Zhu.\u003c/em\u003e\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eAnalysis and interpretation of data: \u003cem\u003eZengqiang Kou, Ke Zhang, Jingning Tang.\u003c/em\u003e\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eDrafting the article: \u003cem\u003eKe Zhang, \u003c/em\u003e\u003cem\u003eJingning Tang, Nan Zhu, Ti Liu.\u003c/em\u003e\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eCritically revising the article: \u003cem\u003eXiaoyu Li, Bei Fan, Wenqi An, Wenjue An, Mingan Dang,\u003c/em\u003e\u003cem\u003eZengqiang Kou, Ruowen Pan.\u003c/em\u003e\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eFinal approval of the version to be submitted: \u003cem\u003eZengqiang Kou, Xiaoyu Li, Ti Liu, Bei Fan, Wenqi An, Wenjue An, Mingan Dang, Ke Zhang, Jingning Tang, Nan Zhu, Ruowen Pan.\u003c/em\u003e\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eProject administration: \u003cem\u003eTi Liu, Nan Zhu\u003c/em\u003e.\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eSupervision: \u003cem\u003eZengqiang Kou, Ruowen Pan\u003c/em\u003e.\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eProvide resources: \u003cem\u003eZengqiang Kou, Wenqi An\u003c/em\u003e.\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eFunding:\u003cem\u003e Wenjue An, Bei Fan\u003c/em\u003e.\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eVisualization: \u003cem\u003eXiaoyu Li\u003c/em\u003e.\u003c/p\u003e\n\u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by Hualan Biological Bacterin Co., Ltd. All authors critically reviewed the draft and provided valuable feedback on the development of this manuscript. The authors are also grateful to the China Shandong Center for Disease Control and Prevention for help with trial implementation.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eSomes, M.P., R.M. Turner, L.J. Dwyer and A.T. Newall, \u003cem\u003eEstimating the annual attack rate of seasonal influenza among unvaccinated individuals: A systematic review and meta-analysis.\u003c/em\u003e Vaccine, 2018. https://doi.org/10.1016/j.vaccine.2018.04.063.\u003c/li\u003e\n\u003cli\u003eYu, H., J. Huang, Y. Huai, X. Guan, J. Klena, S. Liu, et al., \u003cem\u003eThe substantial hospitalization burden of influenza in central China: surveillance for severe, acute respiratory infection, and influenza viruses, 2010-2012.\u003c/em\u003e Influenza and Other Respiratory Viruses, 2014. https://doi.org/10.1111/irv.12205.\u003c/li\u003e\n\u003cli\u003eIuliano, A.D., K.M. Roguski, H.H. Chang, D.J. Muscatello, R. Palekar, S. Tempia, et al., \u003cem\u003eEstimates of global seasonal influenza-associated respiratory mortality: a modelling study.\u003c/em\u003e The Lancet, 2018. https://doi.org/10.1016/s0140-6736(17)33293-2.\u003c/li\u003e\n\u003cli\u003eLi, L., Y. Liu, P. Wu, Z. Peng, X. Wang, T. Chen, et al., \u003cem\u003eInfluenza-associated excess respiratory mortality in China, 2010\u0026ndash;15: a population-based study.\u003c/em\u003e The Lancet Public Health, 2019. https://doi.org/10.1016/s2468-2667(19)30163-x.\u003c/li\u003e\n\u003cli\u003eWang, H., C. Fu, K. Li, J. Lu, Y. Chen, E. Lu, et al., \u003cem\u003eInfluenza associated mortality in Southern China, 2010\u0026ndash;2012.\u003c/em\u003e Vaccine, 2014. https://doi.org/10.1016/j.vaccine.2013.12.013.\u003c/li\u003e\n\u003cli\u003eFeng, L., D.K. Shay, Y. Jiang, H. Zhou, X. Chen, Y. Zheng, et al., \u003cem\u003eInfluenza-associated mortality in temperate and subtropical Chinese cities, 2003\u0026ndash;2008.\u003c/em\u003e Bulletin of the World Health Organization, 2012. https://doi.org/10.2471/blt.11.096958.\u003c/li\u003e\n\u003cli\u003eWu, P., E. Goldstein, L.M. Ho, L. Yang, H. Nishiura, J.T. Wu, et al., \u003cem\u003eExcess Mortality Associated With Influenza A and B Virus in Hong Kong, 1998\u0026ndash;2009.\u003c/em\u003e The Journal of Infectious Diseases, 2012. https://doi.org/10.1093/infdis/jis628.\u003c/li\u003e\n\u003cli\u003eYang, L., S. Ma, P.Y. Chen, J.F. He, K.P. Chan, A. Chow, et al., \u003cem\u003eInfluenza associated mortality in the subtropics and tropics: Results from three Asian cities.\u003c/em\u003e Vaccine, 2011. https://doi.org/10.1016/j.vaccine.2011.09.071.\u003c/li\u003e\n\u003cli\u003eEMEA. NOTE FOR GUIDANCE ON HARMONISATION OF REQUIREMENTS FOR INFLUENZA VACCINES. 1997. https://www.ema.europa.eu/en/harmonisation-requirements-influenza-vaccines. Accessed 04 Mar 2024.\u003c/li\u003e\n\u003cli\u003eFDA-CBER. Clinical Data Needed to Support the Licensure of Seasonal Inactivated Influenza Vaccines. 2007. https://www.fda.gov/regulatory-information/search-fda-guidance-documents/clinical-data-needed-support-licensure-seasonal-inactivated-influenza-vaccines. Accessed 04 Mar 2024.\u003c/li\u003e\n\u003cli\u003eECDC, \u003cem\u003eSystematic review of the efficacy, effectiveness and safety of newer and enhanced seasonal influenza vaccines for the prevention of laboratory-confirmed influenza in individuals aged 18 years and over.\u003c/em\u003e 2020. https://doi.org/10.2900/751620.\u003c/li\u003e\n\u003cli\u003eStassijns, J., K. Bollaerts, M. Baay and T. Verstraeten, \u003cem\u003eA systematic review and meta-analysis on the safety of newly adjuvanted vaccines among children.\u003c/em\u003e Vaccine, 2016. https://doi.org/10.1016/j.vaccine.2015.12.024.\u003c/li\u003e\n\u003cli\u003eGrohskopf, L.A., L.H. Blanton, J.M. Ferdinands, J.R. Chung, K.R. Broder, H.K. Talbot, et al., \u003cem\u003ePrevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices \u0026mdash; United States, 2022\u0026ndash;23 Influenza Season.\u003c/em\u003e MMWR Recomm Rep, 2022. https://doi.org/10.15585/mmwr.rr7101a1.\u003c/li\u003e\n\u003cli\u003eNMPA. Guidelines for the classification of adverse events in clinical trials of preventive vaccines. 2019. https://www.nmpa.gov.cn/xxgk/ggtg/ypggtg/ypqtggtg/20191231111901460.html. Accessed 04 Mar 2024.\u003c/li\u003e\n\u003cli\u003eNMPA. Technical Guidelines for Clinical Research of Seasonal Influenza Virus Vaccine (Exposure Draft). 2021. https://www.cde.org.cn/main/news/viewInfoCommon/237d5f7de6bcfcd08037dcce873794f3. Accessed 04 Mar 2024.\u003c/li\u003e\n\u003cli\u003eHuang, X., T. Fan, L. Li, X. Nian, J. Zhang, X. Gao, et al., \u003cem\u003eSafety and immunogenicity of a quadrivalent, inactivated, split-virion influenza vaccine (IIV4-W) in healthy people aged 3-60 years: a phase III randomized clinical noninferiority trial.\u003c/em\u003e Human Vaccines \u0026amp; Immunotherapeutics, 2022. https://doi.org/10.1080/21645515.2022.2079924.\u003c/li\u003e\n\u003cli\u003eLiu, X., J. Park, S. Xia, B. Liang, S. Yang, Y. Wang, et al., \u003cem\u003eImmunological non-inferiority and safety of a quadrivalent inactivated influenza vaccine versus two trivalent inactivated influenza vaccines in China: Results from two studies.\u003c/em\u003e Human Vaccines \u0026amp; Immunotherapeutics, 2022. https://doi.org/10.1080/21645515.2022.2132798.\u003c/li\u003e\n\u003cli\u003eNational Bureau of Statistics. State Statistics Bureau Bulletin of the seventh national population Census (No.5). 2021. https://www.stats.gov.cn/sj/tjgb/rkpcgb/qgrkpcgb/202302/t20230206_1902005.html. Accessed 04 Mar 2024.\u003c/li\u003e\n\u003cli\u003eQuach, H.Q. and R.B. Kennedy, \u003cem\u003eEnhancing Immunogenicity of Influenza Vaccine in the Elderly through Intradermal Vaccination: A Literature Analysis.\u003c/em\u003e Viruses, 2022. https://doi.org/10.3390/v14112438.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"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":"tropical-diseases-travel-medicine-and-vaccines","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"tdtm","sideBox":"Learn more about [Tropical Diseases, Travel Medicine and Vaccines](http://tdtmvjournal.biomedcentral.com)","snPcode":"40794","submissionUrl":"https://submission.nature.com/new-submission/40794/3","title":"Tropical Diseases, Travel Medicine and Vaccines","twitterHandle":"@BioMedCentral","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Quadrivalent influenza split-virion vaccine, Elderly people, Vaccination, Safety, Immunogenicity","lastPublishedDoi":"10.21203/rs.3.rs-4020018/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4020018/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground \u003c/strong\u003eInfluenza remains a global public health concern. Understanding the vaccination-induced response in an aging population, which is susceptible and at high risk, is essential for disease prevention and control. Here, we report findings on the safety and immunogenicity of a quadrivalent influenza split-virion vaccine (15 µg/subtype/0.5 ml/dose) (hereinafter referred to as the “quadrivalent influenza vaccine”) in a population aged ≥60 years.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods\u003c/strong\u003e This open-label, pragmatic post-marketing trial enrolled 1399 older adults to receive one dose of an approved commercially available quadrivalent influenza vaccine manufactured by Hualan Biological Bacterin Co., Ltd. (hereinafter referred to as “Hualan Bio”). Participants with contraindications for the vaccine were excluded, while poor health condition was acceptable. All vaccinated subjects experiencedadverse events collection within 30 days and serious adverse events within 180 days post-vaccination. 25% subjects, selected randomly, underwent venous blood sampling pre-vaccination and 30 days afterpost-vaccination, for detecting antibody titers against each subtype of influenza virus by hemagglutination inhibition assay. The incidences of adverse events and antibody titers against each subtype of influenza virus were statistically analyzed using SAS 9.4.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e No grade 3 adverse reactions occurred within 30 days post-vaccination. The incidences of overall adverse reactions, local adverse reactions and systemic adverse reactions were 3.79%, 2.86% and 1.00%, respectively. No serious adverse reactions occurred within 180 days post-vaccination. There were 350 subjects who completed venous blood sampling pre-vaccination, among whom 348 subjects completed venous blood sampling at 30 days post-vaccination for immunogenicity assessment. With respect to hemagglutination inhibition antibodies against influenza viruses H1N1, H3N2, BV and BY subtypes, at 30 days post-vaccination, the seroconversion rates were 87.64%, 75.57%, 73.28% and 78.74%, respectively; the seropositive rates were 93.97%, 98.56%, 79.31% and 95.40%, respectively; and the geometric mean increase (GMI) in post-immunization/pre-immunization antibodies was 24.80, 7.26, 10.39 and 7.39, respectively.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion\u003c/strong\u003e One 15 µg/subtype dose of the vaccine had agood safety profile and elicited favorable immunogenicity among subjects aged ≥60 years. The results of this study indicate that Hualan Bio quadrivalent influenza vaccine strike balance between safety and immunogenicity, supporting unnecessity to increase dosage or inoculation frequency for further enhancing immunogenicity.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTrial registration:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eRegistry: Center for drug evaluation, NMPA (\u003ca href=\"http://www.chinadrugtrials.org.cn/\"\u003ehttp://www.chinadrugtrials.org.cn\u003c/a\u003e)\u003c/p\u003e\n\u003cp\u003eRegistration number: CTR20220316.\u003c/p\u003e\n\u003cp\u003eRegistration title: Phase IV clinical study on safety and efficacy of quadrivalent influenza virus split vaccine in larger scale of population.\u003c/p\u003e","manuscriptTitle":"A post-marketing study to evaluate the safety and immunogenicity of a quadrivalent influenza split-virion vaccine in elderly people aged 60 years and older","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-03-21 17:35:46","doi":"10.21203/rs.3.rs-4020018/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-05-29T08:36:26+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-05-24T08:20:37+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"249213515914140350012202576319045800541","date":"2024-05-24T08:08:38+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-05-03T13:26:32+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"265401776413520161985983807631909830176","date":"2024-04-27T23:46:33+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-04-07T16:06:42+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-04-01T11:19:10+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-04-01T11:19:10+00:00","index":"","fulltext":""},{"type":"submitted","content":"Tropical Diseases, Travel Medicine and Vaccines","date":"2024-03-06T08:26:44+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"tropical-diseases-travel-medicine-and-vaccines","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"tdtm","sideBox":"Learn more about [Tropical Diseases, Travel Medicine and Vaccines](http://tdtmvjournal.biomedcentral.com)","snPcode":"40794","submissionUrl":"https://submission.nature.com/new-submission/40794/3","title":"Tropical Diseases, Travel Medicine and Vaccines","twitterHandle":"@BioMedCentral","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"201616af-ab2d-4c41-8801-bd4f2e6228dd","owner":[],"postedDate":"March 21st, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-09-16T16:14:11+00:00","versionOfRecord":{"articleIdentity":"rs-4020018","link":"https://doi.org/10.1186/s40794-024-00228-x","journal":{"identity":"tropical-diseases-travel-medicine-and-vaccines","isVorOnly":false,"title":"Tropical Diseases, Travel Medicine and Vaccines"},"publishedOn":"2024-09-15 15:58:13","publishedOnDateReadable":"September 15th, 2024"},"versionCreatedAt":"2024-03-21 17:35:46","video":"","vorDoi":"10.1186/s40794-024-00228-x","vorDoiUrl":"https://doi.org/10.1186/s40794-024-00228-x","workflowStages":[]},"version":"v1","identity":"rs-4020018","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4020018","identity":"rs-4020018","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}