Impact of age, sex and medical history on adverse reactions to the first and second dose of BNT162b2 mRNA COVID-19 vaccine in Japan: a cross-sectional study

BACKGROUND: Vaccines for coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are being promoted worldwide. In this study, we analyzed the relationship between adverse reactions and the profile of vaccinated recipients. METHODS: Vaccinated subjects who received two doses of BNT162b2 between May 17 and June 11, 2021, at Osaka University Dental Hospital were included in this study. Adverse reactions and profiles were collected by questionnaires, and the relationship between the presence of adverse reactions and the profiles of the vaccinated persons was analyzed by logistic regression analysis. The correlation between the severity of adverse reactions and age was analyzed by Spearman’s rank correlation. RESULTS: Logistic regression analysis showed that, for many kinds of adverse reactions, the incidence was significantly higher in females than in males and in younger than in older people. There was a very weak but significant negative correlation between age and the severity of many kinds of adverse reactions. The relationship between sex and the incidence of each adverse reaction was significant for injection site reactions and fatigue in the first vaccination, whereas significant relationships were found for fatigue, chills, fever, arthralgia, myalgia and headache in the second vaccination, all of which were clearly more likely to occur in females. CONCLUSION: Adverse reactions to BNT162b2 were found to be more frequent and more intense in females and younger people in Japan, especially after the second vaccination.