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

ObjectiveThis 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. MethodsParticipants (n=538; 487 adults and 51 elderly) were enrolled from three public health services in Sao 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. ResultsAmong 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. ConclusionCoronaVac 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 vaccines safety profile.