The shingles vaccine was never meant to protect anyone's brain. It was built to stop a painful rash. But study after study now shows that people vaccinated against shingles face significantly lower dementia risk — and the latest research suggests those already-impressive numbers might be too conservative. A newer, more potent vaccine could deliver even greater protection, while separate findings hint that the shot may slow biological aging itself.
Key Takeaways:
- Multiple large-scale natural experiments across Wales, Australia, and Canada consistently show shingles vaccination reduces dementia rates by roughly 20 percent.
- The newer Shingrix vaccine, which is 90–97 percent effective against shingles, appears to offer even stronger dementia protection than the older Zostavax — one study found a 51 percent lower dementia risk among vaccinated individuals.
- Research published last month suggests shingles vaccination also lowers markers of inflammation and biological aging, offering clues about why the brain benefits exist.
This flood of positive data arrives at a politically awkward moment. The Trump administration, with outspoken vaccine skeptic Robert F. Kennedy Jr. at the helm of health policy, has been pushing back hard against vaccination programs. Meanwhile, the scientific evidence keeps stacking up in the other direction.
The connection between shingles shots and brain health was first noticed years ago. Older adults who received the vaccine seemed to develop dementia at lower rates than those who didn't. Skeptics reasonably pointed to healthy-user bias — maybe people who bother getting vaccinated are simply healthier overall.
Clever study designs quieted that concern. Researchers exploited vaccine rollouts in Wales, Australia, and Canada, where age-based eligibility cutoffs created built-in comparison groups. People couldn't choose which group they landed in. Their birth date decided for them.
The Welsh study, published in Nature in April 2025, tracked over 280,000 older adults after Zostavax became available on September 1, 2013. Adults aged 71 to 78 progressively became eligible. Those who were 80 at rollout were permanently excluded. Over seven years of follow-up, vaccination among eligible adults reduced dementia rates by 20 percent compared to the ineligible group.
In Australia, a study published in JAMA the same month followed more than 18,000 older adults after Zostavax launched on November 1, 2016. People aged 70 to 79 qualified for a free dose. Everyone 80 and older was locked out. After 7.4 years, 5.5 percent of the ineligible group had been diagnosed with dementia versus just 3.7 percent of those eligible — a 1.8 percentage-point difference.
A third study, published this month in The Lancet Neurology, found a similar 2 percentage-point drop in dementia rates following Canada's Zostavax rollout.
As molecular medicine expert Eric Topol of Scripps Research Institute observed, a drug that cut dementia risk by 20 percent would be celebrated as a major breakthrough. The shingles vaccine has achieved comparable results with almost no fanfare.
The original vaccine, though, may have been just the warm-up act. Zostavax, released by Merck in 2006, used a weakened live version of the varicella-zoster virus and reduced shingles risk by 51 percent. In 2017, GlaxoSmithKline introduced Shingrix, a fundamentally different design. Rather than delivering the whole virus, Shingrix uses a single protein from the virus surface — glycoprotein e — paired with an adjuvant that fires up the immune system. Clinical trials showed it was 90 to 97 percent effective at preventing shingles in adults 50 and older.
The CDC switched its recommendation to Shingrix in 2018. And now the dementia data is following the same trajectory.
A 2024 study published in Nature Medicine compared dementia outcomes among over 200,000 Americans vaccinated before or after the Zostavax-to-Shingrix switch. Shingrix recipients enjoyed a 17 percent relative increase in dementia-free time compared to those who received Zostavax.
This month, a study in Nature Communications went further. California-based researchers compared nearly 66,000 Shingrix recipients against more than 260,000 matched unvaccinated controls. The vaccinated group showed a 51 percent lower risk of dementia.
Nobody fully understands why this works. The vaccine targets the varicella-zoster virus — the same pathogen behind childhood chickenpox. Anyone who had chickenpox carries this virus for life, tucked away in nerve cells. When the immune system weakens, typically with age, the virus can reactivate and produce shingles: a painful rash with fluid-filled blisters that can last weeks. In severe cases near the eye or ear, it causes permanent vision or hearing damage.
The leading theory connects vaccination to reduced brain inflammation. By strengthening the immune system's grip on the dormant virus and preventing reactivation, the vaccine may tamp down chronic, low-grade inflammation — a known contributor to neurodegeneration.
A study published last month in the Journal of Gerontology explored this angle directly. Led by Eileen Crimmins and Jung Ki Kim of the University of Southern California, the research examined blood and health markers from over 3,800 adults — roughly half vaccinated, half not. Vaccinated participants showed lower inflammation markers, reduced signs of molecular aging, and better composite biological aging scores.
“Our study adds to a growing body of work suggesting that vaccines may play a role in healthy aging strategies beyond solely preventing acute illness,” Crimmins said.
Kim added a mechanistic perspective: “By helping to reduce this background inflammation—possibly by preventing reactivation of the virus that causes shingles, the vaccine may play a role in supporting healthier aging.”
One persistent pattern in the data deserves attention. Several studies have found women benefit more from the vaccine than men when it comes to dementia protection. The reason remains unclear, but researchers note two potentially related facts: women are more likely than men to develop both dementia and shingles.
The biological aging study hinted at the same gender gap, with vaccinated women performing better on some molecular aging tests.
There's also a ceiling-effect question hovering over all of this research. Most of the major natural experiments relied on Zostavax data, because that vaccine was available during the rollout periods studied. If the far more effective Shingrix delivers proportionally greater brain protection — and early comparisons suggest it does — then the benefits documented so far may represent a floor, not a ceiling.
Additional studies will need to confirm these findings. But the direction of the evidence is remarkably consistent across countries, study designs, and research teams. A vaccine designed to prevent a rash appears to be doing something extraordinary for the brain — and the newer version of that vaccine may do it even better.
Written by Vytautas Valinskas