COVID-19 mRNA vaccination was associated with an increased incidence of myocarditis compared to a background population (IRR 4.18; 95% CI 1.63-8.98), driven entirely by adult males.
Observational (n=7)
Does COVID-19 mRNA vaccination increase the incidence of myocarditis compared to background rates?
COVID-19 mRNA vaccination is associated with a rare but significantly increased risk of mild myocarditis, particularly in adult males, compared to background population rates.
Relative Risk: 4.18 (95% CI 1.63–8.98)
BACKGROUND: Myocarditis following coronavirus disease 2019 (COVID-19) mRNA vaccines (Pfizer-BioNTech and Moderna) has been increasingly reported. Incidence rates in the general population are lacking, with pericarditis rather than myocarditis diagnostic codes being used to estimate background rates. This comparison is critical for balancing the risk of vaccination with the risk of no vaccination. METHODS: A retrospective case series was performed using the Mayo Clinic COVID-19 Vaccine Registry. We measured the incidence rate ratio (IRR) for myocarditis temporally related to COVID-19 mRNA vaccination compared with myocarditis in a comparable population from 2016 through 2020. Clinical characteristics and outcomes of the affected patients were collected. A total of 21 individuals were identified, but ultimately 7 patients met the inclusion criteria for vaccine-associated myocarditis. RESULTS: The overall IRR of COVID-19-related myocarditis was 4.18 (95% confidence interval CI, 1.63-8.98), which was entirely attributable to an increased IRR among adult males (IRR, 6.69; 95% CI, 2.35-15.52) compared with females (IRR 1.41; 95% CI, .03-8.45). All cases occurred within 2 weeks of a dose of the COVID-19 mRNA vaccine, with the majority occurring within 3 days (range, 1-13) following the second dose (6 of 7 patients, 86%). Overall, cases were mild, and all patients survived. CONCLUSIONS: Myocarditis is a rare adverse event associated with COVID-19 mRNA vaccines. It occurs in adult males with significantly higher incidence than in the background population. Recurrence of myocarditis after a subsequent mRNA vaccine dose is not known at this time.
Perez et al. (Mon,) conducted a observational in Myocarditis (n=7). COVID-19 mRNA vaccination vs. Comparable background population from 2016 through 2020 was evaluated on Incidence rate ratio (IRR) for myocarditis (IRR 4.18, 95% CI 1.63-8.98). COVID-19 mRNA vaccination was associated with an increased incidence of myocarditis compared to a background population (IRR 4.18; 95% CI 1.63-8.98), driven entirely by adult males.