Evaluating the Safety Profile of the CoronaVac in Adult and Elderly populations: A Phase IV Prospective Observational Study in Brazil

Objective This Phase IV prospective observational study aimed to evaluate the safety and monitor adverse events following immunization (AEFI) associated with CoronaVac, an inactivated SARS-CoV-2 vaccine, in Brazilian adult (18-59 years) and elderly (≥60 years) populations. Methods Participants (n=538; 487 adults and 51 elderly) were enrolled from three public health services in São Paulo, Brazil. A two-dose vaccination regimen, administered 14 days apart, was used. The study assessed Adverse Reactions (AR) necessitating medical attention within seven days post-vaccination dose and monitored AEFI for a period of 42 days. Safety was monitored through a review of participant diary cards, telephone contacts, and on-site study visits. Results Among adults, the most frequently reported local AR after the first and second dose was pain (256[52.6%] and 129 [29.5], respectively), while the most common systemic reaction was a headache (158[34.5%] and 51 [11.6%], respectively). Most local and systemic solicited ARs were of Grade 1 or 2, with these reactions being more prevalent in adults after the first dose. One serious adverse event possibly related to the vaccine was reported among adults, but there were no fatalities. Nine adult participants experienced adverse events of special interest, which included five cases of Covid-19. Conclusion CoronaVac demonstrated safety and tolerability in the observed population. Ongoing post-marketing surveillance is crucial for the identification of rare adverse events and further affirmation of the vaccine’s safety profile. ### Competing Interest Statement We have read the journal's policy and the authors of this manuscript have the following competing interests: JM is Associate Editor for PLoS One. MC, VI, AL, LR, PB, MS, ML, MO, VG, JM, and FB are current employees of Instituto Butantan. EF is a former employee of Instituto Butantan. ASS, MHL and PJFVB were principal investigators. ### Clinical Trial ClinicalTrials.gov Identifier: [NCT04845048][1] ### Funding Statement The study was funded by Fundação Butantan. Its a civil entity, with private legal status, non-profit, established to support the Instituto Butantan's activities. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The IRB of University São Paulo approved this study (University of São Paulo, IRB protocol number: 4.684.670). The IRB of the collaboating study sites also approved the study. Potential participants were invited to join the study, with participation contingent on signing an informed consent form (writeen informed consent) and agreement to adhere to all study procedures. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data are available in the text and in the supplementary appendix for consultation. [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT04845048&atom=%2Fmedrxiv%2Fearly%2F2023%2F08%2F23%2F2023.08.19.23294316.atom