Myocarditis after COVID-19 and influenza infections: insights from a large data set

In the current issue of Open Heart, the study by Butler and colleagues completed a much-needed investigation that provides valuable insights into the risk of developing incident myocarditis in the general population following COVID-19 or influenza infection. The authors used a large, USA-based administrative health claims database to complete a retrospective analysis of the risk of myocarditis following these infections, including a total of 1 219 185 individuals (adults and children) with documented SARS-CoV-2 infection and 634 201 individuals with influenza. The primary result of the study revealed that, while the overall risk of developing myocarditis is low following these viral infections, the risk is profoundly higher after COVID-19 compared with influenza (0.06% vs 0.02%). These translate to rates of 0.73 and 0.24 myocarditis cases per 1000 person-years, respectively. In agreement with prior reports,1 2 the analysis also found that certain segments of the population are at particularly increased risk for myocarditis post-COVID-19. These include younger males as well as those above 70 years of age. However, the risk distribution for myocarditis was essentially unimodal after influenza, primarily affecting septuagenarians. In addition to age, certain comorbid conditions, including coronary artery disease and prior myocardial infarction, were also established as risk factors in the present analysis.