A RECENT nationwide cohort study conducted in France found that individuals who developed myocarditis after receiving a COVID-19 mRNA vaccine experienced less severe cardiovascular events compared to those with myocarditis of other origins.
The study included 4,635 patients hospitalised for myocarditis between December 27th 2020–June 30th 2022. The research, based on data from the French National Health Data System, identified 558 cases of postvaccine myocarditis (within 7 days after COVID-19 mRNA vaccine), 298 cases of myocarditis following COVID-19 infection (within 30 days of SARS-CoV-2 infection), and 3,779 cases of conventional myocarditis. The occurrence of clinical outcomes (hospital readmission for myopericarditis, other cardiovascular events, all-cause death, and a composite outcome of these events) over the 18 months following hospital admission were analysed using weighted Cox models
Patients who developed myocarditis after vaccination were generally younger, with an average age of 25.9 years, and predominantly male (84%). In contrast, those with post-COVID-19 myocarditis and conventional myocarditis were slightly older, with average ages of 31.0 and 28.3 years, respectively.
At the 18-month follow-up, the study revealed that patients with postvaccine myocarditis had a significantly lower incidence of severe cardiovascular events compared to those with conventional myocarditis. Specifically, the study reported a weighted hazard ratio of 0.55, indicating a 45% reduction in risk for those with postvaccine myocarditis. Conversely, individuals with myocarditis linked to COVID-19 infection had similar outcomes to those with conventional myocarditis.
Despite the generally favourable prognosis for postvaccine myocarditis, the study highlights the necessity for continued medical management for several months after hospital discharge, particularly in young, healthy men who are most affected. These findings are expected to play a critical role in shaping ongoing and future COVID-19 mRNA vaccine recommendations. Monitoring and supporting patients who develop postvaccine myocarditis remains crucial.
Ada Enesco, EMJ
Reference
Semenzato L et al. Long-term prognosis of patients with myocarditis attributed to COVID-19 mRNA vaccination, SARS-CoV-2 infection, or conventional etiologies. JAMA. 2024;DOI:10.1001/jama.2024.16380
