Key result
mRNA COVID-19 booster linked to ~66% lower myocarditis rate versus the second primary dose.
Why the study?
The study aimed to estimate the rate of myocarditis after mRNA COVID-19 booster vaccination by vaccine type, age, and sex.
Does an mRNA COVID-19 booster vaccination have a lower risk of myocarditis compared to the primary series second dose in adults?
Cohort (n=3,459,609)
Does an mRNA COVID-19 booster vaccination have a lower risk of myocarditis compared to the primary series second dose in adults?
Effect estimate: RR 0.34 (95% CI 0.17-0.61)
Absolute Event Rate: 6.08% vs 17.92%
The risk of myocarditis following an mRNA COVID-19 booster dose is rare and significantly lower than the risk following the second dose of the primary series.
May refine myocarditis risk estimates for mRNA doses; leaves open randomized confirmation before guiding practice.
OBJECTIVES: We aimed to estimate the rate of myocarditis after the messenger RNA (mRNA) COVID-19 booster vaccination by vaccine type, age, and sex. METHODS: We used data from the British Columbia COVID-19 Cohort, a population-based cohort surveillance platform. The exposure was a booster dose of an mRNA vaccine. The outcome was diagnosis of myocarditis during hospitalization or an emergency department visit within 7-21 days of booster vaccination. RESULTS: = 0.34, 95% CI: 0.17-0.61). This difference was more apparent for the mRNA-1273 vaccine type. After the second dose, the myocarditis rate in males was significantly lower for BNT162b2 than mRNA-1273 overall and among those aged 18-39 years. In contrast, after the booster dose, no significant differences between myocarditis and vaccine type was observed overall or within the specific age groups among males or females. CONCLUSION: Myocarditis after mRNA COVID-19 vaccines is a rare event. A lower absolute risk of myocarditis was observed after a booster dose of mRNA vaccine than the primary series second dose.
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Naveed et al. (2023) conducted a cohort in Myocarditis (n=3,459,609). mRNA COVID-19 booster vaccine vs. Second dose of mRNA COVID-19 vaccine was evaluated on Rate of myocarditis per million doses within 7 days of vaccination (RR 0.34, 95% CI 0.17-0.61). A booster dose of mRNA COVID-19 vaccine was associated with a significantly lower rate of myocarditis compared to the primary series second dose (RR 0.34).
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