Covid vaccine linked to lower heart attack and stroke risk, study finds

A large Veterans Affairs analysis added a new layer to the Covid vaccine debate: not just whether the shots are safe, but whether they may help lower cardiovascular risk by preventing the infections that can trigger severe heart problems. In a study of 1,039,659 U.S. veterans, researchers found that people who received a 2024-2025 Covid vaccine alongside a flu shot had a 37.7% lower risk of Covid-associated major adverse cardiovascular events after eight months than veterans who got the flu vaccine alone.

The study, published online June 15 in JAMA Internal Medicine, reviewed electronic health records from veterans who had vaccination encounters between September 3, 2024, and December 31, 2024. Of those patients, 349,085 received the Covid vaccine and 690,574 received flu vaccine alone. The main outcome combined cardiovascular death, myocardial infarction, stroke and hospitalization for heart failure, giving the analysis a broader view than simple infection counts or short-term symptoms.

The effect was strongest in older adults. Veterans age 75 and above saw 50.7% vaccine effectiveness against Covid-associated major cardiovascular events, and the benefit was also more pronounced among people with comorbidities. Secondary analyses found even larger absolute reductions when the researchers measured all-cause major adverse cardiovascular events, suggesting the shot’s impact may extend beyond events directly coded to Covid infection.

That broader result is also where the study’s biggest caution lies. The authors said the all-cause protection may reflect Covid infections that were never diagnosed, meaning the vaccine could be reducing heart risk by preventing severe or silent infections rather than acting directly on the cardiovascular system itself. The findings do not prove that vaccination alone eliminates heart attack or stroke risk, and they do not replace individual medical decisions that take age, prior infection, heart disease and other conditions into account.

The study’s authors, led by Ziyad Al-Aly of Washington University in St. Louis and the VA St. Louis Health Care System, estimated the findings could translate into about 3,500 major cardiac events and 2,400 deaths prevented annually per 1 million people. In an accompanying commentary, Robert M. Califf, the former Food and Drug Administration commissioner and a Duke University cardiologist, said updated booster vaccines continue to show protection against major cardiovascular events, hospitalization and all-cause death. Califf also noted that most Americans have now been exposed to the virus, a vaccine or both, and that the country has recorded well over a million Covid deaths.