Does the Shingles Vaccine Lower Dementia Risk? What 4 Studies and a New Trial Show

Table of Contents

• Why a Shingles Vaccine Could Matter for the Brain
• Study 1: The Wales Natural Experiment (Nature, 2025)
• Study 2: The Australian Replication (JAMA, 2025)
• Study 3: The Newer Recombinant Vaccine (Nature Medicine, 2024)
• Study 4: Older Adults After a Nursing-Facility Stay (Annals, 2026)
• The Randomized Trial That Will Decide It
• How Strong Is the Evidence, Really?
• What This Means for You
• FAQ
• References

Why a Shingles Vaccine Could Matter for the Brain

Shingles is caused by the varicella zoster virus, the same virus that causes chickenpox. After a childhood infection it never fully leaves; it stays dormant in nerve tissue and can reactivate decades later, usually when immunity weakens with age. Researchers have long suspected that viral reactivation and the inflammation that comes with it might contribute to brain aging and dementia.

If that is true, a vaccine that prevents reactivation could have a side benefit for the brain. Other explanations are possible too, such as a broader, “off-target” effect of vaccination on the immune system. The challenge has always been proof. People who choose to get vaccinated tend to be healthier and more health-conscious in many ways, which alone could explain lower dementia rates. The studies below are interesting precisely because several of them found clever ways around that problem.

Two vaccines are involved, and the difference matters. The older live-attenuated vaccine (Zostavax) used a weakened live virus. The newer recombinant vaccine (Shingrix) uses a single viral protein plus an immune booster, is given as two doses, and has replaced the live vaccine in the United States and many other countries.

Study 1: The Wales Natural Experiment (Nature, 2025)

When Wales introduced the live shingles vaccine, it used a strict cutoff: people born on or after 2 September 1933 became eligible, and anyone born even one day earlier never did. A Stanford-led team under Pascal Geldsetzer, publishing in Nature in 2025, used this rule as a natural experiment.

The logic is simple. People born one week apart should be almost identical in health and habits. Yet vaccination rates jumped from 0.01% among those who were one week too old to 47.2% among those one week younger. Any difference in dementia between the two groups is therefore very likely caused by the vaccine itself, not by who chose to get it.

Over seven years of follow-up, receiving the vaccine lowered the probability of a new dementia diagnosis by 3.5 percentage points (95% CI 0.6 to 7.1), a 20% relative reduction. The effect was stronger in women than in men. The researchers confirmed the finding in a second dataset, death certificates for England and Wales combined, using deaths with dementia as the main cause.

Study 2: The Australian Replication (JAMA, 2025)

One natural experiment can be a fluke, so the same group looked for another. Australia began offering the live shingles vaccine free to people aged 70 to 79 on 1 November 2016. Anyone who had turned 80 just before that date never became eligible.

Using primary-care records from 65 general practices and 101,219 patients, the team (Pomirchy and colleagues, JAMA 2025) found that being born just after the eligibility threshold (2 November 1936) raised the chance of ever being vaccinated by 16.4 percentage points. Over 7.4 years, eligibility lowered the probability of a new dementia diagnosis by 1.8 percentage points (95% CI 0.4 to 3.3).

Note what that number measures: the effect of being eligible, not of being vaccinated. Because only some eligible people actually got the shot, the effect per vaccinated person is larger. Just as important, eligibility did not change the use of other preventive services or the rates of other chronic diseases, which is a strong sign that the dementia difference is not explained by healthier lifestyles.

Study 3: The Newer Recombinant Vaccine (Nature Medicine, 2024)

Both natural experiments studied the live vaccine, which is no longer used in many countries. Does the recombinant vaccine show the same pattern? A University of Oxford team led by Maxime Taquet and Paul Harrison used another natural experiment: the rapid switch from the live to the recombinant vaccine in the United States.

Comparing people vaccinated just before and just after the switch, the recombinant vaccine was associated with a 17% increase in time without a dementia diagnosis over six years. For people who did go on to develop dementia, that equals about 164 additional days lived without the diagnosis. The association was stronger in women, and the recombinant vaccine also compared favorably with flu and tetanus-diphtheria-pertussis vaccines.

This design is weaker than the date-of-birth experiments because it compares two vaccines rather than vaccinated with unvaccinated people. But it matters for anyone deciding today, because the recombinant vaccine is the one you can actually get.

Study 4: Older Adults After a Nursing-Facility Stay (Annals, 2026)

The newest study, published in Annals of Internal Medicine in July 2026 by Kaleen Hayes, Stefan Gravenstein and colleagues at Brown University, focused on an older and frailer group: 509,926 Medicare beneficiaries aged 66 and over who were admitted to a skilled-nursing facility between 2017 and 2022 (mean age 79). The team used a method called target trial emulation, which structures observational data to mimic a randomized trial as closely as possible.

Only 8,843 people (1.73%) received at least one dose of the recombinant vaccine within 12 months of admission. Over four years, 18.8% of them were diagnosed with dementia compared with 24.6% of those who were not vaccinated, a 5.8 percentage-point difference (risk ratio 0.76, 95% CI 0.69 to 0.84), or 24% lower risk. The association was weaker in men and in people who had previously received the live vaccine.

Two caveats are essential. First, the authors’ own negative-control analyses suggested some residual confounding, meaning healthier people may still have been more likely to get vaccinated. Second, the study’s primary funding came from GlaxoSmithKline, which makes the recombinant vaccine.

The Randomized Trial That Will Decide It

The question will finally be tested properly. In March 2026, GSK started a randomized, placebo-controlled, observer-blind trial in Finland (ClinicalTrials.gov NCT07502560), run with Finnish Vaccine Research. It plans to enroll 33,609 adults aged 76 and older without dementia, randomized 3 to 1 to two doses of the recombinant vaccine or placebo, and to follow them for new dementia diagnoses for up to 10 years. Primary completion is estimated for April 2030.

Until then, every result above is observational, however cleverly designed. The trial is also sponsored by the vaccine’s manufacturer, so independent scrutiny of its results will matter.

How Strong Is the Evidence, Really?

What makes this body of evidence unusual is the convergence. Two independent natural experiments in different countries, a third design using a different vaccine, and a large emulated trial in a frailer population all point in the same direction, with stronger effects in women appearing more than once. That is far more than most “this supplement may lower dementia risk” headlines can claim. It is still not the same as a randomized trial, and the size of any real effect remains uncertain.

It is also worth comparing this with a story we covered recently. In a randomized trial, high-dose DHA reached the brain but did not protect memory at all, as I explained in fish oil pills vs eating fish for brain aging. Observational promise does not always survive a proper trial, which is why the Finnish study matters.

What This Means for You

This is general information, not medical advice. Talk to your doctor about your own vaccination schedule, especially if you are immunocompromised.

• Get the shingles vaccine for the reason it exists. In the United States, the CDC recommends two doses of the recombinant vaccine for adults aged 50 and older. Shingles can be very painful and can leave long-lasting nerve pain; preventing it is reason enough.
• Treat any brain benefit as a bonus, not a promise. The evidence is encouraging and unusually consistent, but it does not prove the vaccine prevents dementia.
• If you had the old live vaccine, ask your doctor whether you should also get the recombinant vaccine. In the nursing-facility study, the association with lower dementia risk was weaker in people who had previously received the live vaccine.
• Keep the proven basics. Immune health is only one piece; as I covered in how to slow immune aging, the immune system’s decline with age is a broader process, and blood pressure, exercise and sleep remain core brain-health priorities.
• Look for consistency, not single headlines. One study rarely settles anything. What makes the shingles evidence stand out is agreement across different designs and countries, the same standard I applied to the multivitamin trials.

FAQ

Does the shingles vaccine prevent dementia?
It may lower the risk, but this is not proven. Four large studies found fewer or later dementia diagnoses in vaccinated groups (20% lower risk in Wales, 24% lower risk in the 2026 US study, 17% more diagnosis-free time in the Oxford study), and two of them used natural experiments that come close to a trial. A randomized trial in Finland started in 2026 and is expected to finish its primary phase around 2030.

Which shingles vaccine was studied?
The Wales and Australia studies looked at the older live vaccine (Zostavax). The 2024 Nature Medicine and 2026 Annals studies looked at the recombinant vaccine (Shingrix), which is the one now used in the US and many other countries.

Why was the effect stronger in women?
Nobody knows yet. The Wales and Oxford studies both found larger effects in women, and the nursing-facility study found weaker associations in men. Possible explanations involve sex differences in immune responses, but this has not been tested directly.

How could a shingles vaccine affect the brain?
Two main ideas are being studied: preventing reactivation of the dormant virus and the inflammation it causes, and broader “off-target” effects of vaccination on the immune system. Neither has been confirmed as the mechanism.

If you want the full system behind how I weigh evidence like this for my own health decisions, I wrote it all down in The MVHK Protocol.

References

• Eyting M, Xie M, Michalik F, Hess S, Chung S, Geldsetzer P. A natural experiment on the effect of herpes zoster vaccination on dementia. Nature. 2025;641:438-446. doi:10.1038/s41586-025-08800-x.
• Pomirchy M, Bommer C, Pradella F, Michalik F, Peters R, Geldsetzer P. Herpes zoster vaccination and dementia occurrence. JAMA. 2025;333(23):2083-2092. doi:10.1001/jama.2025.5013.
• Taquet M, Dercon Q, Todd JA, Harrison PJ. The recombinant shingles vaccine is associated with lower risk of dementia. Nature Medicine. 2024;30:2777-2781. doi:10.1038/s41591-024-03201-5.
• Hayes KN, Harris DA, McConeghy KW, et al. Dementia risk after recombinant herpes zoster vaccination in older adults with a recent skilled-nursing facility stay: a target trial emulation. Annals of Internal Medicine. 2026;179(7):958-967. doi:10.7326/ANNALS-25-04689. PMID 42296498.
• GlaxoSmithKline. A randomized, placebo controlled, observer-blind, phase IV pragmatic trial to evaluate the effect of recombinant zoster vaccine (Shingrix) on incident dementia diagnosis in an older adult population aged 76 years or older in Finland. ClinicalTrials.gov NCT07502560.
• Centers for Disease Control and Prevention. Shingles vaccine recommendations (clinical considerations for recombinant zoster vaccine). cdc.gov, updated 22 October 2024.