Older Adults Who Got a Shingles Vaccine Were Diagnosed With Dementia Less Often

CATEGORY: HEALTHY AGING & LONGEVITY

Adults in Wales who received a shingles vaccine were 20% less likely to be newly diagnosed with dementia over the following seven years—3.5 fewer diagnoses for every 100 people vaccinated—in a study of 282,541 older adults published in Nature.¹ The result carries unusual weight because of how the comparison was made: eligibility for the vaccine was decided by a strict birthdate cutoff, which created two groups of people essentially identical in every way except their access to the shot.

One Week of Birthdate, Two Very Different Chances at a Vaccine

When Wales launched its shingles vaccination program on September 1, 2013, it drew a hard line: anyone born on or after September 2, 1933 could receive the free vaccine, and anyone born earlier never became eligible. Among people born within a single week of that line, vaccination went from 0.01% on the older side to 47.2% on the younger side. Two neighbors born days apart—alike in age, habits, health, and everything else that usually muddies health research—ended up with utterly different odds of getting the shingles vaccine: a lottery run by the calendar. This was not a randomized trial; researchers followed what actually happened to people on either side of the cutoff in Wales’s national health records. But because nobody chooses their own birthdate, the comparison behaves much like an experiment, sidestepping the usual problem that people who seek out vaccines tend to be healthier in other ways too.

Seven Years of Records, 35,307 New Diagnoses

Over the seven years of follow-up, 35,307 of the 282,541 adults in the study were newly diagnosed with dementia—the group of progressive brain diseases, Alzheimer’s disease the most common, that gradually erode memory and thinking. Receiving the vaccine lowered the probability of a new dementia diagnosis by 3.5 percentage points, a relative reduction of 20%. The vaccine also did its ordinary job, cutting shingles episodes by 37.2%. The protection against dementia was clearer in women than in men, in whom the smaller numbers left the result statistically inconclusive—a limit the authors state plainly.

More Protection Than Shingles Prevention Can Explain

The research team set out to test a specific idea: that herpes viruses may be implicated in the development of dementia. Shingles is a painful rash caused when the chickenpox virus, which hides quietly in nerve cells for decades after childhood infection, reawakens later in life. If flare-ups of that virus injure the brain over time, a vaccine that suppresses them might also protect thinking. What the researchers found went beyond their starting hypothesis in one respect: by their own account, the drop in shingles episodes was considerably too small to plausibly account for the size of the drop in dementia diagnoses. That points to the possibility that the vaccine also works through broader effects on the immune system, not just by preventing shingles itself—a mechanism scientists are still working out.

Australia Saw the Same Pattern, and So Did the Newer Vaccine

A finding this striking needs company, and it has some. The same research group examined an almost identical birthdate cutoff in Australia’s vaccine rollout: among 101,219 patients, eligibility for the vaccine went with 1.8 fewer new dementia diagnoses per 100 people over 7.4 years.² And although Wales used the older live vaccine, Zostavax, which has since been discontinued in the United States, a separate Oxford analysis of the newer recombinant vaccine, Shingrix, found it was associated with lower dementia risk than the vaccine it replaced—17% more time lived free of a dementia diagnosis, about 164 extra days, among those eventually affected.³ No randomized trial has yet tested a shingles vaccine against dementia directly; the authors of both natural experiments suggest their results are exactly the kind of evidence that could justify one.

Key Takeaways

• Shingles vaccination went with 20% fewer new dementia diagnoses over seven years in Wales—3.5 fewer per 100 people vaccinated.
• Because a birthdate cutoff decided who could be vaccinated, the compared groups were essentially alike, giving this study more causal weight than ordinary observational research—though it was not a randomized trial.
• Independent findings in Australia and with the newer recombinant vaccine point in the same direction.
• The protection was clearer in women; the data in men were statistically inconclusive.

References

1. 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(8062):438–446. link
2. Pomirchy M, Bommer C, Pradella F, Michalik F, Peters R, Geldsetzer P. Herpes zoster vaccination and dementia occurrence. JAMA. 2025;333(23):2083–2092. link
3. Taquet M, Dercon Q, Todd JA, Harrison PJ. The recombinant shingles vaccine is associated with lower risk of dementia. Nature Medicine. 2024;30(10):2777–2781. link