Prognostic Factors Associated with Fatal Outcomes in COVID-19 Vaccine-Related Myocarditis.

AIMS: Vaccine-related myocarditis (VRM) has gained attention during the global roll-out of COVID-19 vaccines. COVID-19 VRM is usually non-fatal, but factors associated with fatal outcomes remain unclear. We aimed to characterise features associated with reported fatal outcomes using a pharmacovigilance database. METHODS: We retrospectively analysed COVID-19 VRM reports in the Japanese Adverse Drug Event Report database from 2021 to 2024. Reports were stratified into death and survival groups based on recorded outcome information. Logistic regression analyses identified factors associated with reported fatal outcomes. RESULTS: 31,022 reports listed COVID-19 vaccines as suspected drug; 1,041 reports included myocarditis (reporting odds ratio [ROR] 31.3, 95% CI 29.0-33.8). The median time from vaccination to myocarditis onset was 2 (1-4) days, with most events occurring within 7 days. Among reports with VRM, men accounted for the majority (77.8%) and 68.6% were ≤39 years old. Outcome data were available for 863 reports, and death was recorded in 97 reports (11.2% [95% CI, 9.3%-13.5%]). Reported fatal outcomes were more frequent in women, patients aged ≥70 years, those with delayed onset (≥8 days after COVID-19 vaccination), and those with ≥1 comorbidities. Multivariable logistic regression identified age ≥70 years as independently associated with reported fatal outcomes (OR 8.67, 95% CI 4.41-17.3; P < 0.001). CONCLUSIONS: Older age was associated with higher odds of reported fatal outcomes among VRM reports in JADER. Female sex, delayed onset, and comorbidities were more common among reports with fatal outcomes. These exploratory findings require validation in clinically adjudicated studies.