Time-Dependent Changes in Death Reports and the Sex Ratio in the Safety Surveillance of SARS-CoV-2 Vaccination in Japan, the United States, and European Countries

The national safety surveillance of vaccines is a fundamental measure to ensure vaccination safety and maintain transparency and public trust. Our previous study revealed an early increase in death reports after the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination in Japanese surveillance despite our hypothesis that no time-dependent variations in the number of death reports would be seen if the vaccination is not related to serious adverse events. This study is an extensive investigation to determine whether the number of death reports varied consistently over time after vaccination in the older population in Japan, the US, and European countries. We collected the death reports after BNT162b2 mRNA vaccination in individuals aged 65 years or older using the open databases in Japan, the US (Vaccine Adverse Event Reporting System, VAERS), and European countries (EudraVigilance). We observed an early increase of death reports on Day 2 after the vaccination in all three databases. The female-to-male ratio was also assessed and showed a certain degree of time-dependence (R(2) of linear regression 0.54, p =0.01) in Japan but not in the US and European countries. The findings suggest the existence of unknown predictors of the adverse events of the SARS-CoV-2 vaccination, especially for the older Japanese population. The continuous and careful monitoring safety aspects of the vaccines are warranted.