Large study finds strongest link yet between the shingles vaccine and brain health

A large, new study tracked older adults who had received the shingles vaccination and received promising results. The scientists report that those who received a shingles vaccine shot were at a definitive health advantage over the control group.

They were less likely to receive a new dementia diagnosis during the next seven years. The analysis made use of a policy quirk to compare people born just before and after a vaccine eligibility cutoff in 2013. This helped separate cause from coincidence.

Following chickenpox, the varicella-zoster virus (VZV) can go quiet in nerve cells for decades. Later, it can return as herpes zoster, better known as shingles.

After recovery from chickenpox, the virus stays latent in the nervous system and can reactivate as immunity wanes with age.

What the study actually tested

The work was led by Pascal Geldsetzer at Stanford University, who studies large health datasets to answer practical questions in medicine.

His team focused on people who turned 80 in late 2013, because a small birthday difference determined who could get the shingles vaccine that year.

Researchers call this a natural experiment. It was a real-world situation that mimicked a trial because a rule or cutoff split otherwise similar people into different groups.

Those just old enough to miss the program served as a comparison group for those barely young enough to be eligible.

By comparing near identical birth cohorts, the analysis made it less likely that differences in health habits or clinic access explained the result.

That design choice strengthened the case that the shingles vaccine itself mattered for brain outcomes.

“It was a really striking finding,” said Geldsetzer, summarizing the signal they kept seeing across checks and sensitivity analyses.

New shingles vaccine lowers risk more

One idea is simple – fewer viral reactivations may mean less inflammation near nerves and blood vessels that serve the brain.

Another idea is broader – vaccination can tune immune pathways that influence brain health in ways not limited to one microbe.

A 2024 analysis compared the older live vaccine, Zostavax, with the newer recombinant vaccine, Shingrix. Shingrix was associated with a 17 percent lower risk of dementia than Zostavax. It also had a lower risk than other common adult vaccines in similar age groups.

Shingrix includes an adjuvant, a substance that heightens the immune response to a vaccine’s antigen. That extra kick could be one reason the newer shot shows a stronger association with brain outcomes in population data.

Both the Welsh analysis and other large population studies point toward the same conclusion. Shingles vaccination appears to do more than prevent shingles, and the newer recombinant vaccine could be even more effective in lowering dementia risk.

What this means for shingles vaccines

Zostavax used a weakened form of the virus and is no longer the routine shingles vaccine in many places. Shingrix, which is a recombinant vaccine given in two doses, has replaced it in standard adult schedules.

Zostavax and Shingrix both aim to prevent shingles, yet they work differently. Zostavax uses a live, attenuated virus, while Shingrix uses a viral protein plus an adjuvant to train the immune system more directly.

The practical takeaway is simple. A shingles vaccine remains a tool to prevent shingles. Any added protection for brain health is a possible bonus that researchers are still testing, not a reason to treat vaccination as a dementia drug.

Limits and next steps

The Welsh analysis used routine health records, which can miss or delay diagnoses. The design, however, focused on people born only a week apart around the policy cutoff time, which helps balance many hidden differences.

The biology is not settled. Reduced viral reactivation could be part of the story, and immune training unrelated to the virus could be another part. Both are testable in future mechanistic studies.

Dementia affects tens of millions of people. According to a recent WHO factsheet, there are about 57 million people worldwide living with dementia, with nearly 10 million new cases each year.

How to think about risk and causality

Observational studies can be skewed if people who get vaccinated also do other healthy things. This project reduced that concern by using an eligibility threshold to compare very similar groups separated by a quirk of policy.

Even so, the cleanest proof comes from randomized trials that assign the shot or a placebo and follow people over time.

That kind of trial would show whether vaccination delays dementia onset, and by how much, across different ages and risk profiles.

Population level findings are useful for public health decisions. For individuals, the decision to vaccinate should still rest on the proven benefit of preventing shingles and its complications. Any decision should first be discussed with a clinician who knows your medical history.

The study is published in Nature.

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