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Myocarditis, Myopericarditis Risk Up After SARS-CoV-2 Vaccination

But absolute rates of myocarditis or myopericarditis after mRNA COVID-19 vaccination low, even in younger age groups

FRIDAY, Dec. 17, 2021 (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 percent were 12 to 39 years of age, and 73 percent 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 percent confidence interval [CI], 0.90 to 2.00, 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 percent CI, 1.82 to 7.65) and 0.82 (95 percent CI, 0.50 to 1.34), respectively. Among 12- to 39-year-olds, the adjusted hazard ratio was 1.48 (95 percent 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 percent 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 percent CI, 2.11 to 18.96) and 3.22 (95 percent CI, 1.75 to 5.93); the adjusted hazard ratio was 5.24 (95 percent 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.

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