Headlines claiming the “COVID vaccine cuts heart attack risk by 40 percent” have been circulating lately. As a cardiovascular surgeon, I hear this question from patients too. News coverage is often sensational; the actual scientific source is a large observational study in JAMA Internal Medicine, based on US Department of Veterans Affairs (VA) records (Cai et al., JAMA Intern Med 2026). This article summarizes that paper in plain language: what was measured, what was found, what it means — and what it does not mean.
Disclaimer: This article is for general information only; it is not vaccination or treatment advice. Decisions about COVID-19 vaccination and cardiovascular health should always be made with the physician who knows your medical history.
What question did the study ask?
COVID-19 infection can trigger serious cardiovascular events — heart attack, stroke, and heart failure hospitalization — especially in older adults and people with chronic conditions. Earlier data suggested COVID vaccines might lower that risk. Researchers asked: in the 2024–2025 season, with new variants and widespread population immunity, does the updated COVID-19 vaccine still make a cardiovascular difference?
How was the study done?
This was not a randomized clinical trial. It was an observational cohort study using electronic health records (*target-trial emulation*). Between September and December 2024, researchers analyzed 1,039,659 US veterans who received an influenza (flu) vaccine:
- 349,085 people: Same-day 2024–2025 COVID-19 vaccine plus flu vaccine
- 690,574 people: Flu vaccine only (no COVID-19 vaccine)
Mean age was 70.1 years; 91.8% were men. Follow-up lasted about 8 months. Statistical methods were used to balance the two groups, but hidden differences can remain in observational research.
“Heart attack” or a broader outcome bundle?
Headlines often focus on “heart attack” alone. The study’s primary endpoint was MACE (major adverse cardiovascular events) — a combined outcome:
- COVID-19–associated cardiovascular death
- Heart attack (myocardial infarction)
- Stroke
- Hospitalization for heart failure
So the “40% protection” figure refers to the total risk of these four events after a COVID diagnosis, not heart attack in isolation. That gap between headlines and the paper is the most important nuance.
Main findings
Relative risk reduction: about 38%
In the COVID-vaccinated group, COVID-associated MACE risk was 37.7% lower (95% CI 18.2%–54.9%). Media “40 percent” figures likely round this number (Cai et al., 2026).
Absolute benefit: small but real
About 2 fewer events per 10,000 people (95% CI 0.9–3.7). Because events are rare, percentages look dramatic while real-world differences stay modest. That does not mean “the vaccine failed”; it also does not mean “everyone is dramatically protected.”
Strongest signal: age 75 and older
Statistically significant protection for COVID-associated MACE was seen only in people older than 75 (vaccine effectiveness about 50.7%; roughly 5.5 fewer events per 10,000). Results were not significant in those under 65 or aged 65–75. Absolute benefit was greater in people with comorbidities such as diabetes or existing heart disease.
COVID vaccine vs structural coronary disease
This study examines cardiovascular events linked to COVID-19 infection. COVID-19 can increase vascular inflammation, clotting, and arrhythmia risk; vaccination may interrupt that pathway. If you have chronic coronary disease, high cholesterol, or familial cardiac risk, vaccination does not replace ongoing care, medications, or evaluation of arterial disease. When familial hypercholesterolemia is suspected, genetic testing and counseling may also be part of the plan.
Study limitations
- Population: US veterans — older, mostly male; findings may not apply equally to younger women or all countries.
- Design: Observational; we cannot fully separate “vaccine protected the heart” from “vaccinated people differed in other ways.”
- News sources: Newspapers and news aggregators are not scientific references; always check the original peer-reviewed paper.
Practical takeaway
In a large US veteran cohort, the 2024–2025 COVID-19 vaccine was associated with lower risk of serious cardiovascular events after COVID-19 diagnosis: roughly 38% relative reduction, small absolute benefit, clearest in people 75+ and those with chronic illness. That is not the same as “the vaccine prevents 40% of all heart attacks in everyone.” It is a careful reading of current evidence.
Vaccination decisions are personal: age, comorbidities, prior COVID-19, immune status, and concurrent medications all matter. Chest pain, shortness of breath, or other cardiovascular symptoms require urgent medical evaluation regardless of vaccination status.
For an evaluation tailored to your health needs, please reach out via the contact page or read more on the about page.
Scientific References
- Cai M, Xie Y, Al-Aly Z. 2024-2025 COVID-19 Vaccine and Major Adverse Cardiovascular Events Among US Veterans. JAMA Intern Med. 2026. DOI:10.1001/jamainternmed.2026.1929 — doi.org/10.1001/jamainternmed.2026.1929 | PubMed 42295793
