After mRNA-based COVID-19 vaccine administration Between December 2020 and August 2021 in n = 192,405,448 older than 12 years of age in the US During the analytic period BNT162b2 vaccine, 12 years and older mRNA-1273 vaccine, 18 years and over Exposures Vaccination with BNT162b2 (Pfizer-BioNTech) or mRNA-1273 (Moderna) Main Outcomes and Measures Expected rates of myocarditis by age and sex were calculated using 2017-2019 claims data. For persons younger than 30 years of age, medical record reviews and clinician interviews were conducted to describe clinical presentation, diagnostic test results, treatment, and early outcomes. Results Among 192,405,448 persons Receiving a total of 354,100, 845 mRNA vaccines 1,991 reports of myocarditis to VAERS 1,626 met the case definition of myocarditis Of those with myocarditis Median age, 21 years (IQR, 16-31 years) Median time to symptom onset, 2 days (IQR, 1-3 days) Males Comprised 82% of myocarditis cases Reporting rates for cases of myocarditis Within 7 days after COVID-19 vaccination, exceeded the expected rates of myocarditis across multiple age and sex strata Rates of myocarditis were highest after the second vaccination dose Adolescent males aged 12 to 15 years 70.7 per million doses of the BNT162b2 vaccine (One case per 14,144 vaccinations) Males aged 16 to 17 years 105.9 per million doses of the BNT162b2 vaccine (One case per 9,442 vaccinations) Males aged 18 to 24 years 52.4 per million doses of the BNT162b2 vaccine (One case per 19,083 vaccinations) 56.3 per million doses of the mRNA-1273 vaccine (One case per 17,761 vaccinations) Myocarditis in the under 30s 826 cases of myocarditis, who had detailed clinical information available Of these 826 cases of myocarditis 792 of 809 (98%) had elevated troponin levels 569 of 794 (72%) had abnormal electrocardiogram results 223 of 312 (72%) had abnormal cardiac magnetic resonance imaging results Hospital data 784 of 813 (96%) were hospitalized 577 of 661 (87%) had resolution of presenting symptoms by hospital discharge Most common treatment Nonsteroidal anti-inflammatory drugs 589 of 676 (87%). 7.26 + 105.86 = 113.12 Expected, 1.34 113.12 = 84.4 1.34 Supplement
