In a Centers for Disease Control and Prevention (CDC) study, the occurrence of myocarditis inpatient encounters was 42% higher in 2020 than in 2019. The risk for myocarditis among patients with COVID-19 during March 2020–January 2021 was nearly 16 times as high as the risk among patients without COVID-19, with the association between COVID-19 and myocarditis being most pronounced among children and older adults. Further, in this cohort, approximately 40% of patients with myocarditis had a history of COVID-19.
These findings suggest an association between COVID-19 and myocarditis, although causality cannot be inferred from observational data, and are consistent with those from previous studies. Before this report, the two largest known studies, in the United States and in Israel, also found that COVID-19 was strongly associated with myocarditis.
In this study, the association between COVID-19 and myocarditis was lowest for persons aged 25–39 years and higher among younger (<16 years) and older (≥50 years) age groups, a pattern that has not been previously described in age-stratified analyses and that warrants further investigation.
This finding might be partially explained by age-related differences in COVID-19 case ascertainment, because younger adults with less severe disease might be less likely than older adults to have a health care encounter with a COVID-19 diagnosis captured within PHD-SR.
The risk difference for myocarditis between persons with and without COVID-19 was higher among males than among females, consistent with some earlier studies. The finding of a higher risk ratio among females than among males is novel. However, it likely reflects the low risk for myocarditis among female patients without COVID-19.
During March 2020–January 2021, patients with COVID-19 had nearly 16 times the risk for myocarditis compared with patients who did not have COVID-19, and risk varied by sex and age according to a release from MMWR. These findings underscore the importance of implementing evidence-based COVID-19 prevention strategies, including vaccination, to reduce the public health impact of COVID-19 and its associated complications.
Viral infections are a common cause of myocarditis, an inflammation of the heart muscle (myocardium) that can result in hospitalization, heart failure and sudden death. Emerging data suggest an association between COVID-19 and myocarditis. CDC assessed this association using a large, U.S. hospital-based administrative database of healthcare encounters from >900 hospitals.
Data for this study were obtained from the Premier Healthcare Database Special COVID-19 Release (PHD-SR), a large hospital-based administrative database. The monthly number of myocarditis and COVID-19 inpatient encounters was assessed before and during the COVID-19 pandemic, from January 2019 through May 2021.