Although the incidence of myocarditis or pericarditis after mRNA vaccination against COVID-19 is low, a two- to threefold higher probability was observed in individuals who received mRNA-1273 compared with BNT162b2 vaccine, a study revealed.
A group of researchers analyzed data from the British Columbia COVID-19 cohort, a population-based cohort study with the second dose of an mRNA vaccine used as the exposure. The outcome measured was a diagnosis of myocarditis, pericarditis, or myopericarditis during hospitalization or an emergency department visit within 21 days of exposure.
Finally, multivariable logistic regression was used to examine the association between the COVID-19 vaccine and the outcome of interest.
Higher rates of myocarditis and pericarditis per million second doses were noted for mRNA-1273 (n=31; percentage, 35.6, 95 percent confidence interval [CI], 24.1‒50.5; and n=20; rate, 22.9, 95 percent CI, 14.0–35.4, respectively) compared with BNT162b2 (n=28; rate, 12.6, 95 percent CI, 8.4–18.2; and n= 21; incidence, 9.4, 95 percent CI, 5.8–14.4, respectively).
Similarly, mRNA-1273 vaccines had a significantly higher likelihood of myocarditis (adjusted odds ratio [aOR]2.78, 95 percent CI, 1.67–4.62), pericarditis (aOR, 2.42, 95 percent CI, 1.31–4.46), and myopericarditis (aOR, 2.63, 95 percent CI, 1.76–3.93) than BNT162b2.
Men (aOR, 3.21, 95 percent CI, 1.77–5.83) and younger individuals (18–39 years; aOR, 5.09, 95 percent CI, 2.68–9.66), who received mRNA-1273 were more likely to develop myocarditis.
“The rate of myocarditis after receiving mRNA-1273 was highest among younger men (aged 18-39 years) and did not appear to be present at older ages,” the researchers said. “Our findings may have policy implications regarding the choice of vaccine to be offered.”
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