Can the Shingles Vaccine Lower Dementia Risk? A Landmark 2025 Study

Reviewed by the HealthyMag Editorial Team. Last updated: July 2026.

What the 2025 Nature Study Actually Found

In April 2025, the journal Nature published a study titled “A natural experiment on the effect of herpes zoster vaccination on dementia,” led by Markus Eyting and Pascal Geldsetzer at Stanford University, with co-authors Min Xie, Felix Michalik, Simon Heß and Seunghun Chung. Using large-scale electronic health records from Wales, the researchers reported that receiving the shingles vaccine reduced the probability of a new dementia diagnosis over a roughly seven-year follow-up by about 20% in relative terms — an absolute reduction of around 3.5 percentage points (95% confidence interval 0.6 to 7.1 percentage points).

The vaccine involved was Zostavax, the older live-attenuated shingles vaccine that was widely used in the United Kingdom’s rollout during the study period. The primary analysis tracked outcomes from September 2013 through August 2020. Importantly, the researchers found the association held up across a range of checks, and a companion line of work published later in 2025 in the journal Cell reported consistent patterns using the same Welsh natural experiment and additional data from Australia.

Why a “Natural Experiment” Is Stronger Than Ordinary Observational Data

Most of what we read about vaccines and dementia comes from observational studies that simply compare people who chose to get vaccinated with people who did not. The problem is that these two groups differ in many ways. People who seek out vaccines tend to visit doctors more, exercise more, smoke less, and generally look after their health — a pattern researchers call “healthy vaccinee bias.” When such a study finds that vaccinated people get less dementia, it is genuinely hard to know whether the vaccine helped or whether health-conscious people were simply healthier to begin with.

The Welsh study sidestepped much of this problem by exploiting an accident of policy. When the shingles vaccination program launched, eligibility was set by exact date of birth: people born before 2 September 1933 were considered too old and remained permanently ineligible, while those born on or after that date were eligible. The result was a sharp cliff. Among adults who were merely a week too old to qualify, just 0.01% got the vaccine; among those who were a week younger and eligible, 47.2% did.

People born one week apart are, on average, essentially identical in their underlying health, habits and risk factors. The only thing that differed in a big way was their access to the vaccine. This lets researchers compare two nearly matched groups and attribute the difference in dementia rates much more confidently to the vaccine itself. Statisticians call this a regression-discontinuity design, and when it works it delivers evidence that leans toward causation rather than mere correlation. That is a meaningful step up from a standard observational comparison.

Why Might a Shingles Vaccine Affect the Brain?

The idea that a virus and the immune system might play a role in dementia is not new. Shingles is caused by the varicella-zoster virus, the same virus responsible for chickenpox, which stays dormant in nerve cells for life and can reactivate decades later. A related family member, herpes simplex virus type 1 (HSV-1), has been studied for years as a possible contributor to Alzheimer’s disease. In a large 2018 cohort study from Taiwan, Tzeng and colleagues reported that people with HSV infections had a substantially higher risk of later dementia, and that those treated with antiviral medication had a markedly lower risk — a finding that helped fuel the “viral hypothesis” of dementia.

There are several plausible ways a shingles vaccine could fit into this picture, though none is confirmed. One possibility is specific: by preventing reactivation of the zoster virus, the vaccine may reduce viral-driven inflammation and nerve damage that could contribute to dementia over time. Another is broader: live vaccines can produce wide-ranging “trained immunity” effects on the immune system that are not limited to the target virus. Chronic inflammation is itself a recognized feature of the aging brain and of neurodegenerative disease, so anything that dampens it could plausibly matter. The honest position is that researchers have several credible mechanisms but have not yet pinned down which, if any, is doing the work.

The Caveats That Matter

This is genuinely interesting science, but it should be read with care. First, it is one study — even a well-designed one. Extraordinary claims require replication, and while the later Cell work is encouraging, the field is still early. Second, the study measured new dementia diagnoses in people who did not yet have the condition; it says nothing about treating or reversing dementia in someone who already has it. There is no basis here for expecting a shingles shot to restore lost memory or halt established disease.

Third, the effect, while notable, is a reduction in risk, not a guarantee of prevention. Many people who were vaccinated still developed dementia, and many who were not did not. Fourth, the mechanism remains unproven, which means we cannot yet say exactly who would benefit most or why. And finally, the study looked specifically at the older live-attenuated Zostavax vaccine; whether the newer recombinant shingles vaccine (Shingrix), now standard in many countries, produces the same brain-related effect is a separate question that researchers are actively investigating and that this study cannot answer on its own.

The Practical Takeaway

So what should a reasonable person do with this? Not overhaul their health plan based on a single paper — but also not dismiss it. Shingles vaccination is already recommended for older adults on its own merits: shingles is painful, and its most common complication, long-lasting nerve pain, can be debilitating. If a growing body of high-quality evidence suggests the same vaccine may also be associated with a lower risk of dementia, that simply strengthens an already sensible case for staying current on it.

The broader lesson is that routine preventive care can have benefits beyond its obvious target. Vaccines recommended for your age group exist because the balance of evidence favors them, and studies like this one are a reminder that those benefits can sometimes extend further than we first assumed. Whether the shingles vaccine is right for you depends on your age, health history and which vaccine is available where you live — questions best answered with your own doctor.

The takeaway is not that a vaccine cures dementia, but that keeping up with recommended vaccines such as shingles may carry benefits worth discussing with your doctor.

Frequently Asked Questions

Does the shingles vaccine prevent dementia?

Not in any proven, guaranteed sense. The 2025 Nature study found that vaccinated older adults in Wales were about 20% less likely to receive a new dementia diagnosis over seven years — a reduction in risk, not prevention. It is an association from one strong study, and more research is needed before anyone can claim the vaccine “prevents” dementia.

How strong is this evidence?

Stronger than typical vaccine-and-dementia research, but not definitive. Because the study used a date-of-birth eligibility cutoff as a natural experiment, it compared nearly identical groups and could attribute the difference to the vaccine far more confidently than an ordinary observational study. That said, it is still a single study, and its conclusions need independent replication before being treated as settled fact.

Which shingles vaccine was studied?

The study examined Zostavax, the older live-attenuated herpes zoster vaccine used in the UK during the study period. It did not test the newer recombinant vaccine, Shingrix, which is now standard in many countries. Whether Shingrix produces the same possible brain-related benefit is a separate open question researchers are still investigating.

Should I get the shingles vaccine?

For most older adults, shingles vaccination is already recommended to prevent shingles and its painful complications, and this study adds a possible extra reason to stay current. But the right choice depends on your age, health history and which vaccine is available to you. Discuss it with your doctor rather than deciding based on any single study.

Does this help people who already have dementia?

No. The study looked at whether vaccination lowered the chance of a first dementia diagnosis in people who did not yet have the condition. It offers no evidence that a shingles vaccine can treat, slow or reverse dementia that has already developed, and it should not be viewed as a treatment.

Why would a vaccine affect the brain?

Researchers have a few credible theories, none yet proven. The zoster virus can reactivate and cause inflammation, so preventing that may reduce viral-driven damage; alternatively, live vaccines can broadly “train” the immune system in ways that lower harmful inflammation. Related work, such as a 2018 Taiwan study linking herpes infection and antiviral treatment to dementia risk, supports the general viral-inflammation hypothesis, but the exact mechanism remains under study.

Sources

• 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 (published 2 April 2025). https://www.nature.com/articles/s41586-025-08800-x
• Tzeng NS, Chung CH, Lin FH, et al. “Anti-herpetic Medications and Reduced Risk of Dementia in Patients with Herpes Simplex Virus Infections — a Nationwide, Population-Based Cohort Study in Taiwan.” Neurotherapeutics, 2018;15(2):417-429.

This article is for general information and education only and is not medical advice. Talk to a qualified healthcare professional about vaccines and any decisions regarding your health.