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

CATEGORY: HEALTHY AGING & LONGEVITY

In Wales, the date on a birth certificate decided who could get a free shingles vaccine and who never could. Adults who received the shot were 20% less likely to be newly diagnosed with dementia over the following seven years, or 3.5 fewer diagnoses for every 100 people vaccinated, in a study of 282,541 older adults published in Nature.¹ The comparison carries unusual weight, because the two groups were alike in everything except the calendar.

One Week of Birthdays, Two Different Odds of a Shot

Wales launched its shingles vaccination program on September 1, 2013, and drew a hard line through it. Anyone born on or after September 2, 1933 could have the free vaccine. Anyone born a day earlier never became eligible. Among people born within a single week of that line, vaccination ran at 0.01% on the older side and 47.2% on the younger side. Picture two neighbors born days apart, alike in age, habits, health and everything else that usually muddies health research, with utterly different odds of receiving the shingles vaccine. A lottery run by the calendar. Nobody was randomized here; the researchers simply followed what happened to people on either side of the cutoff in Wales’s national health records. But since nobody chooses their own birthdate, the comparison behaves much like an experiment. It sidesteps the usual trouble that people who seek out vaccines tend to be healthier in other ways too.

Seven Years of Records, 35,307 New Diagnoses

Across those seven years, 35,307 of the 282,541 adults were newly diagnosed with dementia, the family of progressive brain diseases that gradually erodes memory and thinking, Alzheimer’s disease being the most common. Vaccination went with a 3.5 percentage point lower probability of such a diagnosis, a relative reduction of 20%. The shot also did its ordinary job, cutting shingles episodes by 37.2%. Protection against dementia showed up more clearly in women. In men the numbers were smaller and the result statistically inconclusive, a limit the authors state plainly.

More Protection Than Shingles Prevention Can Explain

The team set out to test a specific idea: that herpes viruses may play a part in how dementia develops. Shingles is a painful rash that appears when the chickenpox virus, dormant in nerve cells for decades after a childhood infection, reawakens in later life. If those flare-ups injure the brain over time, suppressing them might protect thinking. The data went past that hypothesis in one respect. By the authors’ own account, the drop in shingles episodes was far too small to account for the size of the drop in dementia diagnoses, which points toward broader effects on the immune system that scientists are still working out. Other datasets lean the same way. The same group examined a nearly identical birthdate cutoff in Australia’s rollout, where among 101,219 patients eligibility went with 1.8 fewer new dementia diagnoses per 100 people over 7.4 years.² Wales used the older live vaccine, Zostavax, since discontinued in the United States. A separate Oxford analysis of the newer recombinant vaccine, Shingrix, found it 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 head on. The authors of both natural experiments say their results are 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.
• A birthdate cutoff, not a choice, decided who could be vaccinated, so the compared groups were essentially alike. That gives 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 the same direction. The protection was clearer in women; in men the data 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