Cohort study
Booster vaccination with SARS-CoV-2 mRNA vaccines and myocarditis in adolescents and young adults: a Nordic cohort study
- Multinational cohort study
- nationwide registers
- Denmark, Finland, Norway and Sweden
- country-specific results combined in meta-analyses
Authors' conclusion
The results suggest that a booster dose is associated with increased myocarditis risk in adolescents and young adults. However, the absolute risk of myocarditis following booster vaccination is low.
Study context
- Population
- 12-to-39-year-olds in Denmark, Finland, Norway and Sweden1,533 myocarditis cases
- Participants
- 8.9 million participants
- Exposure
- 28-day acute risk period after third mRNA dose vs post-acute period ≥28 days after second dose
- Outcome
- Inpatient diagnosis of myocarditis (adjusted IRR)
- Follow-up
- 28 days after third dose
Main finding
As reported in the abstract
Myocarditis, males 12–39 y · 28 days
Each group vs post-acute second doseIncidence rate ratio (95% CI)
Third dose BNT162b2
2.08(1.31–3.33)
Third dose mRNA-1273
8.89(2.26–35.03)
Observational data: associations, not effects.
Further findings
| Outcome | Third dose BNT162b2 | Third dose mRNA-1273 | Post-acute second dose | IRR (95% CI) | |
|---|---|---|---|---|---|
| Myocarditis, females (subgroup) · 28 days · only estimable for BNT162b2 | 0.15 (95% CI 0.04–0.39) events per 100 000 vaccinated | Not reported in the abstract | Not reported in the abstract | 3.99 (0.41–38.64) | |
| 0.050.21520Incidence rate ratio (log scale) |
Death within 30 days of vaccine-related cases
- No deaths within 30 days of vaccine-related cases
Original publication
Booster vaccination with SARS-CoV-2 mRNA vaccines and myocarditis in adolescents and young adults: a Nordic cohort study. Eur Heart J. Published 15 February 2024. doi:10.1093/eurheartj/ehae056
Summarised from the published abstract; every number is checked against it