The latest study of the 2024-2025 COVID-19 vaccine in U.S. veterans finds an association with fewer serious cardiovascular events, showing lower rates of heart-related death, heart attack, and heart-failure hospitalizations among those who got the updated COVID shot alongside their flu vaccine compared with those who only got flu shots.
Researchers used Department of Veterans Affairs records to compare veterans who received the COVID vaccine and flu shot the same day to a larger group that received only the flu vaccine, creating a direct way to look for vaccine-associated differences in heart outcomes. The two groups were large and real-world, with nearly 350,000 people in the same-day group and about 700,000 in the flu-only group, which lets the analysis pick up modest but meaningful signals. That scale matters because cardiovascular events are relatively uncommon and need big numbers to detect changes. The study tracked outcomes for roughly eight months after vaccination.
Average age in the study hovered around 70 and the population was predominantly male, which reflects the veteran pool but limits how directly the results apply to younger, more gender-balanced populations. Within that follow-up window, the data showed a relative vaccine effectiveness of 37.7% against COVID-associated major adverse cardiovascular events, a composite measure the authors used to capture the most serious heart-related outcomes. Because the study was observational, it cannot prove the vaccine caused the reductions, only that vaccination was linked with lower event rates. Still, the association is clear enough to warrant attention from clinicians and patients alike.
Breaking down the composite, the investigators reported a 57.9% lower risk of cardiovascular death among those who received the COVID shot, a 38.5% lower risk of heart attack, and a 41.9% lower risk of hospitalization for heart failure compared with the flu-only group. The result for stroke did not reach statistical significance, so the evidence there is inconclusive rather than definitively negative. Those component differences suggest the vaccine’s benefit was not uniform across every type of cardiovascular outcome but leaned heavily toward preventing the most lethal and hospitalization-driving events. The practical takeaway is that vaccinated veterans in this analysis faced fewer of the acute, life-threatening cardiac complications associated with COVID.
Age mattered: people 75 and older saw the largest benefit, with a 50.7% effectiveness estimate for preventing COVID-associated major adverse cardiovascular events in that subgroup. The vaccine’s impact also appeared stronger in veterans with preexisting health conditions, suggesting that those at higher baseline cardiovascular risk may gain the most from avoiding severe COVID or blunted infections. Those patterns fit with the idea that preventing infection or reducing its severity will have an outsized payoff for people already vulnerable to cardiac complications. It also highlights why targeting higher-risk groups for updated immunization can be an efficient public-health move.
Experts caution that changing viral behavior and population immunity could blunt observable benefits and complicate interpretation of observational data. Lower clinical severity from newer variants, widespread prior infection in unvaccinated people, and falling rates of COVID testing all make it harder to link a later heart event to a specific infection. That mix of factors likely explains why the magnitude of benefit here was smaller than in some earlier studies done earlier in the pandemic when variants were more virulent and prior immunity was rarer. Observational designs can adjust for many things, but residual confounding and unmeasured differences always remain possible.
Dr. Glenn Hirsch called these results “not overall surprising” in an interview. “This result is consistent with previous studies of the COVID-19 vaccine and other vaccines against infectious diseases [in] preventing cardiovascular events, including heart attack, cardiovascular cause of death or hospitalizations,” he said. “This is an observational trial and there can always be some confounding after necessary statistical adjustments and other potential benefits or harms, including adverse effects from vaccines that were not investigated in this study,” he added.
“This can lead to a higher risk of blood clotting, but can also make arterial plaques susceptible to rupture, which then leads to clot formation to heal a ruptured plaque,” he said. “This clotting can cause a near-total or complete occlusion of an artery, leading to these cardiovascular events.” “Vaccines either prevent infection or reduce the severity of infection and subsequent inflammation, lowering the cardiovascular risk.”
