U.S, 29 June 2021, Montgomery et al, JAMA Cardiology
In this case series of 23 male patients, including 22 previously healthy military members, myocarditis was identified within 4 days of receipt of a COVID-19 vaccine. Each patient had a final diagnosis of myocarditis without infectious, ischemic, or autoimmune etiologies identified. All patients presented with acute chest pain and significantly elevated cardiac troponin levels (10-fold to 400-fold the upper limits of their respective reference ranges). Their symptoms began within 12 to 96 hours following immunization with an mRNA COVID-19 vaccine. Sixteen had received the mRNA-1273 vaccine (Moderna), and 7 had received the BNT162b2-mRNA vaccine (Pfizer-BioNTech). For all but 3 patients, the second dose of vaccine preceded their myocarditis presentations. Echocardiography in 4 patients (17%) demonstrated reduced left ventricular ejection fractions (40% to 50%).