The Shingles Vaccine Keeps Showing Up in Dementia Research

Most dementia research runs into the same wall. People who get vaccinated, exercise and see their doctor regularly tend to differ in many ways from people who do not, and no amount of statistical adjustment fully separates the habit from the person. That is why a set of findings on the shingles vaccine has drawn so much attention from researchers who are usually skeptical of this kind of claim.

A birthday that decided who got the shot

When Wales introduced a shingles vaccination program on September 1, 2013, supply was limited, so officials drew a hard line. People born on or after September 2, 1933, were eligible. People born before that date were not, and never would be.

That rule created what economists call a natural experiment. A person who turned 80 a week before the cutoff and a person who turned 80 a week after it are, on average, the same in every way that matters for dementia. The only systematic difference was access to the vaccine.

A team led by Markus Eyting and Pascal Geldsetzer used that line to study health records for older adults in Wales. Their paper in Nature¹, published in April 2025, found that receiving the vaccine reduced the probability of a new dementia diagnosis over seven years by 3.5 percentage points. That works out to a 20 percent relative reduction². By 2020, about one in eight people in the cohort, then in their mid 80s, had been diagnosed with dementia.

The effect appeared stronger in women than in men. They reported a similar signal in a second dataset from England that used deaths from dementia as the outcome.

The newer vaccine shows a similar pattern

The Welsh program used Zostavax, a live attenuated vaccine. The United States stopped using it in 2020 in favor of Shingrix, a two-dose recombinant vaccine that is far more effective against shingles itself.

A separate team at the University of Oxford took advantage of the fast switch from one vaccine to the other in the United States. In a 2024 study in Nature Medicine³, they compared more than 100,000 people vaccinated just after the switch with a similar number vaccinated just before it.

Over six years, Shingrix recipients had 17 percent more time free of a dementia diagnosis than people who got the older vaccine. Among those who did develop dementia, that equaled about 164 extra diagnosis-free days. According to the university's summary⁴, Shingrix was also linked to 23 to 27 percent lower risk than flu or tetanus vaccines. Here too, the effect was larger in women.

Why a shingles shot might matter for the brain

Shingles is caused by the varicella zoster virus, the same virus that causes chickenpox. After childhood infection it stays dormant in nerve tissue for life and can reactivate as immunity weakens with age.

Researchers have proposed several ways that could affect the brain. Reactivations may cause inflammation in blood vessels and nerve tissue, and some laboratory work links herpes viruses to the amyloid and tau proteins found in Alzheimer's disease. Shingrix also contains an adjuvant that stimulates the immune system broadly, which the Oxford authors noted could play a role of its own.

None of these mechanisms has been confirmed in people. They are plausible explanations that would need to be tested.

What this means for patients now

The practical question is simpler than the science. The CDC recommends⁵ two doses of Shingrix, given two to six months apart, for adults 50 and older with healthy immune systems, and for adults 19 and older with weakened immune systems. The recommendation stands on its own, because shingles can be severe and the nerve pain that follows it, called postherpetic neuralgia, can last for months or years. In adults 50 to 69, the vaccine was 97 percent effective at preventing shingles in trials, and 91 percent effective in those 70 and older.

You should get the vaccine even if you have already had shingles, received the old Zostavax shot or are not sure whether you had chickenpox. There is no upper age limit. Since 2023, Medicare Part D plans have covered recommended adult vaccines, including Shingrix, without cost sharing, and pharmacies across Rhode Island give it.

The dementia findings are best seen as a possible bonus, not the reason to get vaccinated. Researchers involved in both studies have called for a randomized trial. Until one exists, the honest summary is that the shingles vaccine prevents a painful disease, and that some of the best observational evidence in the field suggests it may also lower the odds of a dementia diagnosis.