(HealthDay News) — SARS-CoV-2 mRNA vaccination is associated with a significantly increased risk for myocarditis or myopericarditis among males and females receiving mRNA-1273 and among females receiving BNT162b2, but absolute rates are low, according to a study published online Dec. 16 in The BMJ.
Anders Husby, M.D., Ph.D., from Imperial College London, and colleagues conducted a population-based cohort study involving 4,931,775 individuals aged 12 years or older followed from Oct. 1, 2020, to Oct. 5, 2021, to examine the association between severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination and myocarditis or myopericarditis.
The researchers found that 269 participants developed myocarditis or myopericarditis during follow-up; 40% were 12 to 39 years of age, and 73% were male. Forty-eight of the 3,482,295 individuals vaccinated with Pfizer BioNTech BNT162b2 developed myocarditis or myopericarditis within 28 days of vaccination (adjusted hazard ratio, 1.34; 95% confidence interval [CI], 0.9 to 2, compared with unvaccinated individuals; absolute rate, 1.4 per 100,000 vaccinated individuals); the adjusted hazard ratios among females only and males only were 3.73 (95% CI, 1.82 to 7.65) and 0.82 (95% CI, 0.5 to 1.34), respectively.
Among 12- to 39-year-olds, the adjusted hazard ratio was 1.48 (95% CI, 0.74 to 2.98). Twenty-one of the 498,814 individuals vaccinated with Moderna mRNA-1273 developed myocarditis or myopericarditis within 28 days of vaccination (adjusted hazard ratio, 3.92; 95% CI, 2.30 to 6.68, compared with unvaccinated individuals; absolute rate, 4.2 per 100,000 vaccinated individuals).
Among women only and men only, the adjusted hazard ratios were 6.33 (95% CI, 2.11 to 18.96) and 3.22 (95% CI, 1.75 to 5.93); the adjusted hazard ratio was 5.24 (95% CI, 2.47 to 11.12) among 12- to 39-year-olds.
“The clinical outcomes after myocarditis or myopericarditis events were predominantly mild, providing evidence to support the overall safety of SARS-CoV-2 mRNA vaccines,” the authors write.
One author disclosed financial ties to the pharmaceutical industry.
