How does the risk of myocarditis or stroke after COVID‑19 vaccination compare to the risk after COVID‑19 infection in adults over 65?
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Executive summary
COVID-19 infection carries a substantially higher risk of myocarditis and other cardiac complications, including in older adults, than does vaccination; population studies in multiple countries report larger absolute and relative increases in myocarditis after SARS‑CoV‑2 infection than in the weeks after mRNA vaccination [1] [2] [3]. For stroke, large registry analyses in older populations show either neutral long‑term stroke risk after vaccination or decreased stroke incidence—benefits attributed to protection from COVID‑19—while COVID‑19 infection itself is linked to increased short‑ and long‑term risk of ischemic events [4] [5] [6].
1. Infection vs. vaccine: myocarditis—magnitude and direction of risk
Meta‑analyses and national registry studies converge on a clear pattern: myocarditis risk is higher after SARS‑CoV‑2 infection than after COVID‑19 vaccination, often by substantial margins; one systematic review found the relative risk of myocarditis was about 15‑fold after infection versus about twofold after vaccination in pooled studies [1], and national analyses in England reported a substantially greater risk in the four weeks after infection than after vaccine doses [3]. Large surveillance across U.S. healthcare systems likewise found cardiac complications—including myocarditis—were significantly more likely following infection than following mRNA vaccination across age and sex strata [2]. While several studies documented an elevated, short‑term myocarditis signal after mRNA doses—especially in younger males—those vaccine‑linked events were numerically modest and generally milder than infection‑associated myocarditis in available cohorts [7] [8] [9].
2. What changes when the focus is adults over 65
The balance of evidence shows that older adults face a higher absolute cardiac risk from COVID‑19 infection than younger groups, and some analyses specifically report that infection‑related myocarditis or pericarditis risk is greater in older adults than in those under 40 [10]. Vaccination studies in high‑risk older cohorts show neutral or reduced rates of major cardiovascular events (including stroke) over 1–2 years and preserved vaccine effectiveness against severe COVID‑19 in the 65+ strata [4] [11]. However, most myocarditis‑after‑vaccine signals are concentrated in younger males, so the incremental myocarditis risk attributable to vaccination in adults over 65 appears small compared with the larger myocarditis risk posed by infection [7] [8] [10].
3. Stroke: vaccine effects, infection effects, and older age
Large cohort and registry analyses suggest vaccination does not increase long‑term stroke risk and may reduce stroke incidence indirectly by preventing COVID‑19; a Swedish nationwide study and other European cohorts reported decreased risks for several major cardiovascular outcomes after vaccination—especially following booster doses—with no consistent signal for increased stroke after vaccination and even some dose‑dependent protection [4] [5]. By contrast, COVID‑19 infection is associated with increased short‑term and longer‑term risk of ischemic events, and studies examining post‑infection outcomes report elevated occurrences of acute myocardial infarction and ischemic stroke following COVID‑19 [6]. For adults over 65—who already carry higher baseline stroke risk—the protective effect of vaccination against COVID‑19 therefore translates into at least neutral and often reduced stroke risk at the population level [4] [5].
4. Severity, timing, and clinical context matter
Myocarditis after vaccination typically appears within days and is concentrated after certain doses and in younger males, while myocarditis after infection can be more frequent and more severe, with higher rates of hospitalization and death seen in some cohorts [1] [9]. For stroke and other ischemic events, much of the benefit shown after vaccination is plausibly mediated by prevention of infection and its pro‑thrombotic, inflammatory sequelae; some long‑term observational studies in vaccinated older adults report neutral stroke risk at two years, while other registries show incremental protection with additional doses—differences that may reflect study design, population age, and vaccine uptake patterns [4] [5].
5. Limitations, alternative interpretations, and practical takeaways
The evidence base is large and multi‑national but heterogeneous: many studies pool broad age ranges or focus on younger groups for myocarditis signals, and not all datasets disaggregate precise absolute rates for the 65+ cohort, so quantifying exact per‑100,000 risks for that age group from the supplied sources is limited [1] [7] [4]. Nonetheless, converging analyses—from meta‑analyses to national registries and health‑system surveillance—consistently show infection poses a greater myocarditis risk than vaccination and that vaccination is neutral to protective for stroke at the population level in older adults, largely because vaccination prevents severe COVID‑19 and its vascular complications [1] [2] [5] [3]. Policymakers and clinicians should weigh the small, dose‑ and age‑dependent myocarditis risk after mRNA vaccines against the larger, age‑amplified cardiac and cerebrovascular risks of COVID‑19 infection when advising adults over 65 [11].