Myocarditis After COVID-19 Vaccination in Those Under 21: A Generally Mild, Treatable Condition

Myocarditis is a rare adverse event following COVID-19 vaccination, most often affecting males younger than 30. Although vaccine-associated myocarditis appears to be significantly less common than COVID-19–associated myocarditis (NEJM JW Cardiol Jul 2021 and JAMA Cardiol 2021 May 27; [e-pub]), coverage in the lay press has fueled vaccine hesitancy. Truong et al retrospectively collected data on 139 adolescents and young adults who experienced myocarditis within 30 days of COVID-19 vaccination at 26 centers in the U.S. and Canada (median age, 15.8 years, 90.6% male, 66.2% white, 20.9% Hispanic).

In all, 136 of 139 cases occurred after mRNA vaccination, with 131 following the Pfizer/BioNTech vaccine; 128 occurred after the second dose. Symptoms began a median 2 days after vaccination, with chest pain being almost ubiquitous. Most patients received NSAIDs; other treatment options included IVIG, glucocorticoids, and colchicine. Median length of hospital stay was 2 days (range, 0–10 days); 26 patients required ICU care, 2 required inotropic/vasoactive support, and none required ECMO or died. All had elevated troponin, 97 had EKG abnormalities, and 7 had non-sustained ventricular tachycardia. Ejection fraction <55% was seen in 26 patients, all of whom showed normalized ejection fraction on follow-up echocardiograms. Gadolinium enhancement and myocardial edema were seen in most of those undergoing cardiac MRI a median 5 days from symptom onset.