Myocarditis Following a COVID-19 Messenger RNA Vaccination: A Japanese Case Series

COVID-19 vaccine-related myocarditis has been reported worldwide. We herein report two Japanese cases with suspected vaccine-related myocarditis. A 27-year-old man was admitted with chest pain 4 days after the second vaccination. An electrocardiogram (ECG) did not reveal any significant abnormalities. The second patient, a 37-year-old man, was admitted with chest pain 9 days after the first vaccination. His ECG exhibited ST-elevation in multiple leads. In both cases, cardiac magnetic resonance imaging findings were consistent with myocarditis. They recovered with symptomatic relief within a few days. These cases suggest that the benefit of COVID-19 vaccination exceeds the risk of vaccine-related myocarditis.