Cohort Study: Lower Risk of Cardiovascular Complications in Post–COVID-19 Vaccine Myocarditis Compared to Conventional Etiologies

Study Design and Population: This French nationwide cohort study included 4,635 individuals aged 12-49 hospitalized for myocarditis between December 2020 and June 2022. The cohort was divided into three groups: 558 patients with post–COVID-19 mRNA vaccine myocarditis, 298 with post–COVID-19 infection myocarditis, and 3,779 with conventional myocarditis.

Main Findings: At 18 months of follow-up, the frequency of cardiovascular events was significantly lower in the postvaccine myocarditis group (5.7%) compared to conventional myocarditis (13.2%) with a weighted hazard ratio (wHR) of 0.55 (95% CI, 0.36-0.86). Hospital readmission for myopericarditis occurred in 3.2% of postvaccine cases, 4.0% of post–COVID-19 cases, and 5.8% of conventional cases. The all-cause mortality rate was 0.2% for postvaccine myocarditis, 1.3% for post–COVID-19 myocarditis, and 1.3% for conventional myocarditis.

Implications for Practice: Postvaccine myocarditis patients, primarily young males, experience fewer complications compared to conventional myocarditis, but long-term follow-up is still needed. These findings should guide future mRNA vaccine recommendations and clinical management for myocarditis patients.

Reference: Semenzato L. et al. (2024). Long-term Prognosis of Myocarditis Attributed to COVID-19 mRNA Vaccination, SARS-CoV-2, or Conventional Etiologies. JAMA, Online. DOI: http://doi.org/10.1001/jama.2024.16380

Link: https://jamanetwork.com/journals/jama/fullarticle/2822933