Recombinant shingles vaccine linked to 9% lower cardiovascular disease burden in older adults

In 2017, the United States made a quiet switch. The live shingles vaccine that had protected older adults for over a decade gave way to a new recombinant version. That transition, unremarkable at the time, created something researchers rarely get: a natural experiment. By comparing people who received one vaccine or the other during a narrow window around that shift, scientists could isolate the effect of vaccine type itself—stripped of the usual confounding factors that plague vaccine studies.

A team analyzing electronic health records from across the US healthcare system followed 72,920 adults aged 60 and older, matching them carefully on age, health status, and other characteristics. Half received the live attenuated vaccine in the spring and summer of 2017, when it still dominated. The other half received the recombinant vaccine a year later, when it had become standard. The groups were nearly identical in every measurable way except for which vaccine they got. Over the next seven years, researchers tracked their cardiovascular outcomes.

The findings, published in Nature Medicine, surprised even the researchers. Those who received the recombinant vaccine carried a 9 percent lower burden of cardiovascular disease overall. The benefit was clearest for heart failure and ischemic heart disease—both reduced by roughly 10 to 12 percent across both men and women. Atrial fibrillation, an irregular heartbeat that raises stroke risk, also declined by 7 percent. Ischemic stroke showed no significant overall reduction, though men who received the recombinant vaccine had 12 percent fewer strokes. The associations were strongest in the first few years after vaccination and weakened over time.

What makes this finding noteworthy is not just the numbers but the method. Traditional vaccine studies compare people who chose to get vaccinated against those who didn't—a comparison muddied by the fact that health-conscious people are more likely to seek vaccines in the first place. This study sidestepped that trap. The two groups had similar preventive healthcare use, similar cardiovascular risk profiles, and similar medication patterns before and after vaccination. The only meaningful difference was the vaccine itself.

The mechanism remains unclear. The recombinant vaccine contains an adjuvant called AS01 designed to boost immune response. Researchers hypothesize it may alter how immune cells function in ways that protect blood vessels and reduce inflammation—specifically by dampening interleukin-6 responses, a marker linked to cardiovascular risk. But these immune effects may fade, which could explain why the protective association weakened in later years. The study cannot prove causation; unmeasured factors like diet, smoking, and socioeconomic status could still play a role, and all outcomes relied on diagnoses recorded in electronic health records.

The researchers were careful about their claims. They note that while the natural-experiment design is stronger than conventional observational studies, it still falls short of the gold standard: a randomized controlled trial. They call for exactly that—prospective clinical trials to confirm whether the recombinant vaccine truly prevents cardiovascular events, and mechanistic studies to understand how. If the finding holds, it would reshape how we think about shingles vaccination in older adults. A vaccine already recommended for its protection against shingles pain could also reduce heart attacks and heart failure—a secondary benefit that might matter enormously at the population level.