Reactogenicity after the first and second doses of BNT162b2 mRNA coronavirus disease vaccine: a single-center study

This study was conducted to determine differences in adverse events associated with the first and second doses of the BNT162b2 coronavirus disease 2019 vaccine based on the age and sex of recipients.

An online survey on the post-vaccination adverse events of healthcare workers was conducted from March 2021 to April 2021. The differences in the types of adverse events, including severity, onset time, and duration of symptoms, and how the adverse events were dealt with by the patient were analyzed based on the age and sex. The profiles of adverse events were compared after the first and second vaccination doses.

Among the 131 participants who participated in the online survey out of 208 vaccine recipients, 43 and 80 recipients of the BNT162b2 vaccine experienced adverse events after the first and second dose, respectively. No sex-related differences were observed in the profiles of adverse events in vaccinated recipients. The overall frequency of adverse events did not differ based on age after the first dose. After the second dose, the frequency of adverse events, including both local and systemic reactions was significantly higher in the younger age group than in the older age group.

The BNT162b2 vaccine resulted in a higher frequency of adverse events after the second dose than after the first dose especially in the younger age group; however, no sex-related differences associated with these adverse events were observed.