Comprehensive Assessment of Adverse Events Following CoronaVac Immunization: A Population-based Study in Turkey Between January and August 2021

Abstract

Objective:The principal aim of this study was to rigorously assess the incidence and characteristics of adverse events following the administration of CoronaVac, an inactivated viral vaccine, which was one of the first pandemic vaccines to gain regulatory approval for emergency use in Turkey and is among the most widely administered vaccines globally for containment of the COVID-19 pandemic. Methods:We conducted a longitudinal, population-based study of individuals who received two doses of the CoronaVac vaccine at intervals of 0 and 28 days between January 14, 2021, and August 1, 2021. This study employed a prospective design to collect and analyze data on adverse events occurring within a one-month follow-up period after the first and second dose administration. Results:The cohort comprised 2,446 individuals, with a gender distribution of 51.2% females and 48.8% males, with an average age of 43.54 ± 15.90 years. The incidence of adverse events was 19.5% following the first dose and decreased to 15.6% after the second dose. Notably, females demonstrated a statistically higher rate of adverse events than males for both the first and second doses. Concurrently, individuals with comorbidities such as hypertension and diabetes exhibited significantly fewer side effects than those without comorbidities. The most commonly reported adverse events included arm pain, injection site pain, and fatigue. Only a small percentage of individuals required medical intervention and no hospitalizations were attributed to vaccineinduced adverse effects. Conclusion:Given that all reported adverse events were of mild-to-moderate severity and completely resolved, it can be provisionally concluded that the vaccine has an acceptable safety profile. However, for a more definitive interpretation of the vaccine's long-term safety, further studies with extended follow-up periods are imperative.