STEMI Mimic: Focal Myocarditis in an Adolescent Patient After mRNA COVID-19 Vaccine

Background: In May 2021, the U.S. Food and Drug Administration expanded the Emergency Use Authorization for the Pfizer-BioNTech mRNA Coronavirus disease 2019 (COVID-19) Vaccine (BNT162b2) to include adolescents 12–15 years of age. As vaccine administration continues to increase, potential adverse outcomes, to include myocarditis, are being reported to the Vaccine Adverse Event Reporting System. Case Report: This case report describes a 17-year-old male patient who developed focal myocarditis mimicking an ST-segment elevation myocardial infarction (STEMI) 3 days after administration of an mRNA COVID-19 vaccine. Why Should an Emergency Physician Be Aware of This? Myocarditis is a rare complication in adolescents receiving mRNA COVID-19 vaccines. Focal myocarditis may demonstrate localizing electrocardiographic changes consistent with a STEMI. Overall, complications of the mRNA COVID-19 vaccines are extremely rare. The vaccine continues to be recommended by public health experts, as the benefits of vaccinations greatly outweigh the rare side effects.