Shingles vaccine cut major cardiac events nearly in half among heart disease patients

The shingles vaccine was designed to prevent a painful rash. It may also be one of the most effective cardiac interventions available to older adults.

A study of nearly 247,000 US adults with atherosclerotic heart disease found that those who received the shingles vaccine had 46% fewer major adverse cardiac events over the following year compared with matched unvaccinated individuals. They were 66% less likely to die from any cause. Heart attacks dropped 32%. Strokes fell 25%. Heart failure was 25% less common. The findings, being presented at the American College of Cardiology's Annual Scientific Session (ACC.26) in New Orleans, add to a growing body of evidence that the vaccine's benefits extend far beyond preventing shingles.

Comparable to quitting smoking

The magnitude of the risk reduction is substantial. Lead author Robert Nguyen, MD, a resident physician at the University of California, Riverside, noted that the cardiac protection seen in the study is comparable to the cardiovascular benefit of quitting smoking - one of the most powerful risk-reduction strategies in cardiology.

Previous research had shown that shingles vaccination was associated with a 23% lower risk of cardiovascular events in the general population, with cardioprotective effects potentially lasting up to eight years. The current study focused specifically on people who already had heart disease - the highest-risk group - and found that the protective association was even stronger in these patients.

The clotting connection

The biological mechanism is thought to involve blood clots. Shingles infections have been linked to the formation of clots around the brain and heart, raising the risk of heart attacks, strokes, and venous thromboembolism. The herpes zoster virus, which causes shingles, reactivates from dormancy in the nervous system, and the resulting inflammation appears to trigger a prothrombotic state - an increased tendency for blood to clot. By preventing the infection, the vaccine may also prevent these dangerous clotting events.

The Centers for Disease Control and Prevention recommends the shingles vaccine for all adults aged 50 and older, as well as younger adults with weakened immune systems. The current study's population - adults over 50 with established atherosclerotic disease - represents precisely the group most vulnerable to both shingles complications and cardiovascular events.

Study design and numbers

The researchers used TriNetX, a database containing health records of millions of Americans, to identify adults aged 50 and older with atherosclerotic disease between 2018 and 2025. They matched 123,411 vaccinated individuals (who had received at least one dose of either Shingrix or Zostavax) with an equal number of unvaccinated individuals, controlling for demographics and health conditions.

Cardiac events were assessed between one month and one year after vaccination (or the equivalent time period for the unvaccinated group). The one-month washout period excluded any immediate post-vaccination effects, focusing the analysis on the medium-term cardiovascular outcomes.

The healthy vaccinee problem

There is an important caveat. People who get vaccinated tend to be healthier than those who do not, for reasons that have nothing to do with the vaccine itself. They may be more likely to exercise, eat well, attend regular medical appointments, and manage chronic conditions. This is known as the healthy vaccinee effect, and it can inflate the apparent benefit of any vaccine in observational studies.

The researchers controlled for several health behaviors and socioeconomic factors, including housing, employment, education, and literacy. But it is impossible to fully account for every lifestyle difference between vaccinated and unvaccinated populations in a retrospective analysis. The study may therefore overestimate the portion of risk reduction that is directly attributable to preventing shingles infections.

That said, the study's large size - nearly a quarter of a million participants - and its statistical methodology still support a high degree of confidence that the shingles vaccine is associated with a meaningful reduction in cardiovascular risk. The consistency of the findings across multiple endpoints (heart attack, stroke, heart failure, and all-cause mortality) further strengthens the association.

One year of data, a lifetime of questions

The study tracked outcomes only during the first year after vaccination. Whether the cardiac protection persists, strengthens, or wanes beyond that window is unknown from this dataset. A 2025 study suggested the protective effects in the general population may last up to eight years, but comparable long-term data in high-risk cardiac patients do not yet exist.

A randomized controlled trial - rather than a retrospective observational study - would provide stronger evidence of a causal relationship. Until such a trial is conducted, the association, however consistent, remains correlational.

For clinicians, the practical takeaway is straightforward: the data provide another reason to ensure that eligible patients receive the shingles vaccine, particularly those with existing cardiovascular disease who stand to benefit the most.