Myocarditis Following SARS-CoV2 mRNA Vaccination Against COVID-19: Facts and Open Questions

Acute myocarditis most commonly results from a viral infection, with an age-standardized incidence of 40 per 100,000 subjects.1 Common upper respiratory viruses, enteroviruses, human herpesvirus 4 and 6, parvovirus B19, and others can induce exaggerated inflammation in the heart, mainly in young men with a certain immune and genetic susceptibility.1 Myocarditis as well as pericarditis may also rarely occur after vaccination, as observed with the large vaccination programs against influenza, hepatitis B, or smallpox, and more recently with the worldwide vaccination program against SARS-CoV-2.2, 3, 4, 5 In particular, messenger RNA (mRNA)–based technology vaccines (Moderna mRNA-1273 and less so Pfizer-BioNTech BNT162b2) may trigger self-limited and mild myocarditis in 1 to 5 in 100,000 vaccinated individuals. Still, the benefit-risk assessment for COVID-19 (mRNA) vaccination against COVID-19–related hospitalizations, intensive care unit admission, and death underscores a very strong favorable balance of vaccination for all age and sex groups—starting from adolescence—despite this minor risk.6,7 COVID-19 vaccination also reduces the danger of myocardial injury (and myocarditis) or arrhythmias (reviewed in Rosano et al8).