A pharmacoepidemiological study of myocarditis and pericarditis following mRNA COVID-19 vaccination in Europe

PurposeTo assess myocarditis and pericarditis reporting rate as adverse drug reactions (ADRs) for the messenger ribonucleic acid (mRNA) coronavirus disease 2019 (COVID-19) vaccines authorized in Europe. MethodsData on myocarditis and pericarditis related to mRNA COVID-19 vaccines (period: January 1, 2021 - February 11, 2022) were collected from the EudraVigilance database and combined with the European Centre for Disease Prevention and Controls (ECDC) vaccination tracker database. The reporting rate was expressed as 1 million individual vaccinated-days with a corresponding 95% confidence interval (CI), and an observed-to-expected (OE) analysis was performed to check if there was an excess risk for myocarditis or pericarditis following mRNA COVID-19 vaccination. ResultsThe reporting rate of myocarditis per 1 million individual vaccinated-days in the study period was 17.27 (95% CI, 16.34-18.26) for the CX-024414 vaccine and 8.44 (95% CI, 8.18-8.70) for TOZINAMERAN vaccine. The reporting rate for pericarditis per 1 million individual vaccinated-days in the study period was 9.76 (95% CI, 9.06-10.51) for the CX-024414 vaccine and 5.79 (95% CI, 5.56-6.01) for TOZINAMERAN vaccine. The OE analysis showed that both vaccines produced a myocarditis standardized morbidity ratio (SMR) greater than 1, with the CX-024414 vaccine having a greater SMR than TOZINAMERAN. Regarding TOZINAMERAN, SMR for pericarditis was greater than 1 when considering the lowest background incidence, but smaller than 1 when considering the highest background incidence. ConclusionsOur results suggest an excess risk of myocarditis following the first dose of mRNA COVID-19 vaccine, but the relationship between pericarditis and mRNA COVID-19 vaccine remains unclear.