Risk of myocarditis is higher following a SARS-CoV-2 infection than it is following a COVID-19 vaccination and increases significantly in men under 40 years, particularly following a second dose of mRNA-1273 vaccine. The risk is still modest following sequential doses or a booster of BNT162b2 mRNA vaccine. These are among the study findings published in Circulation.
Researchers sought to evaluate risk for myocarditis in younger people following sequential doses of COVID-19 vaccine vs risks of myocarditis in all individuals who develop SARS-CoV-2 infection.
Researchers conducted a self-controlled case series study in England from December 2020 through mid-December 2021 to evaluate if a link exists between COVID-19 vaccination and myocarditis, stratified by age and sex.
They found that among almost 43 million individuals aged at least 13 years, receiving at least 1 dose of vaccine (half receiving 3 doses), there were almost 6 million individuals who developed SARS-CoV-2 infection before or after vaccination. Of these patients, 2861 experienced myocarditis, of which 617 events occurred within 28 days following vaccination.
Risk for myocarditis increased within 28 days following a first dose of ChAdOx1 (incidence rate ratio [IRR], 1.33; 95% CI, 1.09-1.62) and a first dose of BNT162b2 (IRR, 1.52; 95% CI, 1.24-1.85), a second dose (IRR, 1.57; 95% CI, 1.28-1.92), and booster dose of BNT162b2 (IRR, 1.72; 95% CI, 1.33-2.22). This risk was lower than the risk following a positive SARS-CoV-2 test before vaccination (IRR, 11.14; 95% CI, 8.64-14.36) or following vaccination (IRR, 5.97; 95% CI, 4.54-7.87).
Myocarditis risk was greater within 28 days after a second dose of mRNA-1273 (IRR, 11.76; 95% CI, 7.25-19.08) and continued following a booster dose (IRR, 2.64; 95% CI, 1.25-5.58).
Men younger than 40 years faced stronger associations for all vaccines and excess myocarditis events per million people was greater after a second dose of mRNA-1273 than after a positive SARS-CoV-2 test (97; 95% CI, 91-99; vs 16; 95% CI, 12-18). The number of excess events per million among women younger than 40 years was almost identical following a second dose of mRNA-1273 (7; 95% CI, 1-9) vs a positive test (8; 95% CI, 6-8).
“…the risk of myocarditis is greater after SARS-CoV-2 infection than after COVID-19 vaccination and remains modest after sequential doses including a booster dose of BNT162b2 mRNA vaccine,” the study authors wrote.
This article originally appeared on The Cardiology Advisor
Patone M, Mei XW, Handunnetthi L, et al. Risk of myocarditis after sequential doses of COVID-19 vaccine and SARS-CoV-2 infection by age and sex. Circulation. Published online August 22, 2022. doi:10.1161/CIRCULATIONAHA.122.059970