As SARS-CoV-2 continues to circulate in a population shaped by years of infection and vaccination, a foundational public health question has lingered: do updated COVID-19 vaccines still protect against the cardiovascular complications that made the virus so dangerous in its early years? New evidence from one of the largest contemporary analyses to date suggests the answer is yes — though the magnitude of protection has narrowed considerably, and the greatest gains now accrue to those at highest clinical risk.
The research, published in JAMA Internal Medicine, was led by scientists at the VA St. Louis Health Care System and Washington University School of Medicine. It looked at more than one million U.S. veterans to see whether the 2024-2025 COVID-19 vaccine reduced serious heart problems — heart attacks, heart failure, and cardiovascular death, collectively known as major adverse cardiovascular events, or MACE. It’s one of the largest real-world looks yet at how well current vaccines protect the heart, and it comes as health officials continue to weigh how strongly to recommend annual COVID-19 shots.
Researchers compared veterans who got both the COVID-19 vaccine and a flu shot on the same day against those who got only the flu shot. The final group included just over one million people, with an average age of 70, tracked for about eight months.
The vaccine was linked to a 38% drop in COVID-related MACE overall — about two fewer events for every 10,000 people vaccinated. Broken down further, it was associated with a 58% reduction in cardiovascular deaths, a 39% reduction in heart attacks, and a 42% reduction in heart failure hospitalizations.
The benefit wasn’t evenly spread. Among people over 75, the vaccine cut MACE risk roughly in half — a much bigger effect than in younger groups, where the numbers pointed the same direction but weren’t statistically solid. People with heart disease, kidney disease, or diabetes also saw larger real-world gains, even though the relative risk reduction looked similar across groups.
Perhaps the most striking numbers came from a broader look at all-cause outcomes — not just cases formally tied to a COVID diagnosis, but all heart events, hospitalizations, and deaths during the study period. Here, the gap was much wider: about 24 fewer MACE events, 30 fewer hospitalizations, and 16 fewer deaths per 10,000 vaccinated people. Applied to a population of one million, the researchers estimate vaccination could plausibly prevent around 2,370 cardiovascular events and 1,580 deaths over eight months. Those are modeled estimates from observational data, not a guarantee, but they hint at a burden that’s easy to miss when only confirmed COVID cases are counted.
The study suggests a lot of vaccine-preventable heart damage is going undetected by systems that only track confirmed infections. If true more broadly, that means COVID’s cardiovascular toll, and the value of vaccination in reducing it, may be substantially undercounted in official surveillance.
The findings also give policymakers a data point for prioritizing outreach: the benefit was clearest and largest in people over 75 and those with existing heart, kidney, or metabolic conditions — groups where the case for vaccination remains strongest.
Study caveats: The VA population skews older, white, and male, so the results may not translate perfectly to the broader public, though the analysis did include meaningful numbers of women, younger veterans, and non-White participants. The researchers also didn’t break results out by virus variant, and they assumed getting a flu shot at the same time doesn’t change how well the COVID vaccine works — an assumption that hasn’t been directly tested.
Sources and further reading:
Cai M, Xie Y, Al-Aly Z. 2024-2025 COVID-19 Vaccine and Major Adverse Cardiovascular Events Among US Veterans. JAMA Internal Medicine. June 15, 2026.