Objective
This study aimed to characterize the clinical presentation, short term prognosis, and myocardial
tissue changes associated with acute myocarditis following COVID-19 vaccination in the
pediatric population.
Methods
In this retrospective multicenter study across 16 US hospitals, patients <21 years of age with a
diagnosis of myocarditis following COVID-19 vaccination were included and compared to a
cohort with the multisystem inflammatory syndrome in children (MIS-C). Younger children with
vaccine-associated myocarditis were compared to older adolescents.
Results
63 patients with a mean age of 15.6 years were included. 92% were male. All had received an
mRNA vaccine and, except for one, presented following the 2nd dose. Four patients had
significant dysrhythmia. 14% had mild left ventricular dysfunction on echocardiography which
resolved on discharge. 88% met the diagnostic cardiac magnetic resonance (CMR) Lake Louise
criteria for myocarditis. Myocardial injury was more prevalent in comparison to MIS-C patients.
None of the patients required inotropic, mechanical, or circulatory support. There were no
deaths. Follow-up data obtained in 86% of patients, at a mean of 35 days showed resolution of
symptoms, arrhythmias, and ventricular dysfunction.
Conclusions
Clinical characteristics and early outcomes are similar between the different pediatric age
groups. There is evidence of myocardial inflammation and injury following mRNA COVID-19
vaccination as seen on CMR. The hospital course is mild with quick clinical recovery and
excellent short-term outcomes. Close follow up and further studies are needed to understand the
long-term implications and mechanism of these myocardial tissue changes
