Cumulative Adverse Event Reporting of Anaphylaxis After mRNA COVID-19 Vaccine (Pfizer-BioNTech) Injections in Japan: The First-Month Report

Introduction In mid-February, the nationwide immunization plan for the prevention of coronavirus disease 2019 (COVID-19) started in Japan (at first primarily focused on health professionals) using an mRNA-based vaccine (Pfizer/BioNTech). During the phase-in period from February to March, attention was focused on post-vaccination anaphylaxis and anaphylactoid symptoms from the viewpoint of ensuring the safety of the vaccination program. Objective The aim of this report was to provide an update on the status of anaphylaxis and anaphylactoid symptoms occurring after vaccination for COVID-19, as reported under the Adverse Event Following Immunization (AEFI) reporting system in Japan. Methods The Pharmaceutical and Medical Devices Agency (PMDA) received AEFI reports from health professionals and manufacturers under the reporting system for AEFI after vaccination for COVID-19, which has been in operation since mid-February 2021. Reported AEFIs of anaphylaxis and anaphylactoid symptoms were assessed using the Brighton Collaboration Criteria to assess diagnostic certainty. Results 1-month since Japan started the vaccination program for COVID-19 in February 2021, 578,835 doses have been administered to health professionals, with the PMDA receiving 181 suspected event reports of anaphylaxis and anaphylactoid symptoms. In 171 of these 181 cases, women developed these symptoms. Among 181 cases evaluated according to the Brighton Collaboration Criteria, 47 cases (26%) were classified as level 1-3 (reporting rate: 8.1/100,000 doses). Conclusion The results appear similar to reported AEFIs in foreign studies of coronavirus vaccine administration to health professionals, although the reporting rate was higher. Further work is needed to examine the causal relationship of anaphylaxis reactions to coronavirus vaccine administration. Issues of multiple reporting and possible sex/age bias also remain to be analyzed.