Abstract

Objective: Considering the classical vaccine development processes, COVID-19 vaccines were developed in a concise period. However, safety cannot be compromised for the rapid development of vaccines. Therefore, we aimed to investigate and compare the incidence of acute adverse events between vaccine doses and vaccine types in patients who were previously diagnosed with COVID-19 and those who were not.  

Method: The study was conducted prospectively between July 1, 2021, and October 31, 2021. Participants who were vaccinated with the Pfizer-BioNTech BNT162b2 mRNA COVID-19 vaccine and the Sinovac inactivated SARS-CoV-2 vaccine (CoronaVac) were recruited in the cohort study. The cohort was divided into two vaccine categories and sub-branches: those with COVID-19 in each vaccine category and those without. Eight days after the vaccination, all participants in the cohort were provided with an assessment questionnaire regarding the adverse events they experienced. 

Results: A total of 1607 vaccine doses were followed in the study, 18.7% (n=301) of which were the inactivated SARS-CoV-2 vaccine and 81.3% (n=1306) were the BNT162b2 vaccine. According to the statistics, the risk of developing adverse events with the BNT162b2 vaccine was shown to be 5.8 times higher than the inactivated SARS-CoV-2 vaccine (OR: 5.83; 95% CI: 4.34-7.84). In addition, the risk of suffering such adverse events was 1.6 times higher in patients who were previously diagnosed with COVID-19 (OR: 1.61; 95% CI: 1.29-2.00) as opposed to patients who were not.

Conclusion: Based on the results, we can conclude that acute adverse events were more prevalent after vaccination with the BNT162b2 vaccine than the inactivated SARS-CoV-2 vaccine. Furthermore, compared to those who did not have COVID-19, it was evident that patients who were previously diagnosed with COVID-19 were prone to experience mild, temporary, and manageable adverse events.