Does a COVID mRNA booster raise myocarditis risk?
In England, myocarditis admissions rose mainly in males 16–39 within 0–6 days after mRNA doses (highest after dose 2); boosters still elevated risk but prior infection lowered vaccine-associated RIs.
Source
Risk of myocarditis and pericarditis after a COVID-19 mRNA vaccine booster and after COVID-19 in those with and without prior SARS-CoV-2 infection: A self-controlled case series analysis in England
Inspect source passages
Does a COVID mRNA booster raise myocarditis risk?
These passages occur verbatim in the stored paper text. They support the points listed below; they do not verify every statement in the explanation.
2,284 myocarditis and 1,651 pericarditis admissions in the study period.
There were 2,284 admissions for myocarditis and 1,651 for pericarditis in the study period.
ChAdOx1-S first-dose RI 5.23 (95% CI 2.48–11.01).
For ChAdOx1-S, an elevated RI was only observed after a first dose, RI 5.23 (95% CI [2.48, 11.01]; p < 0.001).
What they did
Ran a nationwide self-controlled case series comparing admission risk windows after BNT162b2, mRNA-1273, and ChAdOx1-S doses and after SARS-CoV-2 infection, stratified by age, sex, dose, and prior infection.
What they found
2,284 myocarditis and 1,651 pericarditis admissions. Elevated vaccine RIs mainly in 16–39-year-olds 0–6 days post-dose, especially males. ChAdOx1-S elevation only after first dose (RI 5.23). Prior infection lowered second-dose RIs; infection itself raised risk over 1–27 days.
The limits
What it doesn't show
Hospital-admission SCCS estimates rare absolute risks incompletely for mild outpatient cases; does not weigh COVID benefits vs risks for individuals.
Key terms
- Self-controlled case series
- Method comparing incidence in risk windows vs control time within the same person.
- Relative incidence (RI)
- Ratio of event rate in post-exposure risk windows versus baseline windows.
- BNT162b2
- Pfizer-BioNTech COVID-19 mRNA vaccine.
- mRNA-1273
- Moderna COVID-19 mRNA vaccine (higher priming mRNA dose).
- ChAdOx1-S
- Oxford-AstraZeneca adenovirus-vectored COVID-19 vaccine.
- Booster dose
- Additional mRNA dose after a primary series; risk still elevated but generally lower than dose 2.
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Myocarditis admissions numbered about:
Common questions
How many myocarditis admissions?
2,284 (plus 1,651 pericarditis).
Who had elevated vaccine RIs?
Mainly 16–39-year-olds, especially males, 0–6 days postvaccination.
ChAdOx1-S pattern?
Elevated RI only after first dose (RI 5.23).
Effect of prior infection?
Lower vaccine-associated RIs than in infection-naive vaccinees.