Myocarditis and pericarditis in individuals exposed to the Ad26.COV2.S, BNT162b2 mRNA, or mRNA-1273 SARS-CoV-2 vaccines.

Importance: There is a high level of public and professional interest related to potential safety issues of the COVID-19 vaccines; however, no serious adverse cardiovascular events were reported in phase 3 randomized controlled trials of their safety and efficacy. Moreover, none of the case series from the United States (US) of these potential complications have been population-based.

Objectives: To estimate the reporting rates of myocarditis and pericarditis in the US using the Vaccine Adverse Event Reporting System (VAERS), and to assess if these adverse events were disproportionally reported among the different COVID-19 vaccines.

Design Setting And Participants: All cases of myocarditis and pericarditis from VAERS reported up to July 28, 2021.

Exposure: Single-dose Ad26.COV2.S, BNT162b2 mRNA, or mRNA-1273 SARS-CoV-2 vaccinations.

Main Outcomes And Measures: Reporting rates were computed by dividing the total number of cases of myocarditis and pericarditis (combined) by the total number of vaccine doses administered. Disproportionality analyses were performed to evaluate disproportional reporting of myocarditis and pericarditis for the Ad26.COV2.S and mRNA-1273 vaccines vs. the BNT162b2 mRNA vaccine.

Results: By July 28, 2021, 1392, 699, and 68 cases of myocarditis or pericarditis had been reported out of 1.91, 1.38, and 1.33 million administered doses of the BNT162b2 mRNA, mRNA-1273, and Ad26.COV2.S COVID-19 vaccines, respectively. Median times to event were 3 days, 3 days, and 9 days for the BNT162b2 mRNA, mRNA-1273, and Ad26.COV2.S COVID-19 vaccines. The reporting rates for myocarditis or pericarditis were 0.00073 (95% confidence interval, 95% CI 0.00069-0.00077), 0.00051 (95% CI 0.00047-0.00055), and 0.00005 events per dose (95% CI 0.00004-0.00006) for the BNT162b2 mRNA, mRNA-1273, and Ad26.COV2.S COVID-19 vaccines, respectively. Myocarditis and pericarditis were disproportionally reported following the BNT162b2 mRNA vaccine when compared with the other vaccines, using both disproportionality measures.

Conclusions And Relevance: We found reporting rates of myocarditis and pericarditis to be less than 0.1% after COVID-19 vaccination. Rates were highest for the BNT162b2 mRNA vaccine, followed by the mRNA-1273 and Ad26.COV2.S, respectively. However, the reporting rates of myocarditis and pericarditis secondary to vaccination remains less common than those seen for SARS-CoV-2 infection.