Myocarditis, pericarditis not uncommon with mRNA-1273 COVID-19 vaccines

Although the incidence of myocarditis or pericarditis following mRNA COVID-19 vaccination is low, a two- to threefold higher likelihood is seen among individuals who received mRNA-1273 compared to BNT162b2 vaccine, reveals a study.

A group of researchers analysed data obtained from the British Columbia COVID-19 Cohort, a population-based cohort study, with the second dose of an mRNA vaccine used as exposure. Outcome measured was diagnosis of myocarditis, pericarditis, or myopericarditis during a hospitalization or an emergency department visit within 21 days of the exposure.

Finally, multivariable logistic regression was used to examine the relationship between 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; rate, 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; rate, 9.4, 95 percent CI, 5.8‒14.4, respectively).

Likewise, mRNA-1273 vaccines had a significantly greater 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 following mRNA-1273 receipt is highest among younger men (age 18-39 years) and does not seem to be present at older ages,” the researchers said. “Our findings may have policy implications regarding the choice of vaccine offered.”