Monitoring of Adverse Events Associated with COVID-19 Vaccine (Tozinameran) -Influence of Sex, Age, and Number of Doses on the Frequencies of Adverse Reactions-

Abstract

This study was aimed at monitoring the adverse reactions to tozinameran (mRNA vaccine against SARS-CoV-2) in the vaccine recipients, and to investigate factors that might affect the risk of development of these reactions. The adverse events (13 injection-site and systemic reactions) on day 1 (vaccination day), day 2, day 3, day 4, and day 5- were monitored in the employees of Fukuoka City Hospital who were vaccinated at the hospital between March 2021 and April 2021. The severities of the adverse reactions were also investigated. The frequencies of virtually all the adverse reactions were the highest on day 2, both after the first and after the second dose. The incidence of adverse reactions on day 2 after the first (and second) vaccine dose was 86.0% (86.9%) for pain at the injection site, 33.2% (76.9%) for fatigue, 14.3% (56.9%) for headache, 37.0% (57.2%) for myalgia, 5.2% (51.1%) for fever, and 9.3% (43.9%) for joint pain. The proportion of recipients with any adverse reactions on day 5- was significantly higher after the second dose than after the first dose. The incidence of moderate to severe adverse reactions (except for pain and swelling at the injection site, and rash) was also significantly higher after the second dose. Differences in the incidence of adverse reactions by sex, age, and number of doses were observed. In particular, female sex, age 55 years or under, and second vaccine dose were associated with a significantly increased incidence of fatigue and headache. Female sex and second vaccine dose were identified as being consistently associated with an increased frequency of adverse reactions. The results of the present study would be useful for predicting adverse reactions in prospective recipients, and for setting the vaccination day.