Shingles Vaccine Protects Against Dementia

A flagship study came out in Nature in 2025 that solidified a long observed finding, that the Shingles (Herpes Zoster) vaccine can protect against dementia.

Previous studies were classic observational cohort designs which can fail to show causation or account for confounding factors. This 2021 study found "a combined analysis estimated a 31% lower risk" and indicated the need for stronger research.

In comes the 2025 Nature study, this time a natural experiment arose:

To provide causal as opposed to correlational evidence, we take advantage of the fact that, in Wales, eligibility for the zoster vaccine was determined on the basis of an individual’s exact date of birth. Those born before 2 September 1933 were ineligible and remained ineligible for life, whereas those born on or after 2 September 1933 were eligible for at least 1 year to receive the vaccine.

The finding:

We show that receiving the zoster vaccine reduced the probability of a new dementia diagnosis over a follow-up period of 7 years by 3.5 percentage points (95% confidence interval (CI) = 0.6–7.1, P = 0.019), corresponding to a 20.0% (95% CI = 6.5–33.4) relative reduction. This protective effect was stronger among women than men.

Interestingly, the newer recombinant vaccines seem to be ever more effective than the live-attenuated vaccines (the ones tested in the Nature experiment), though more studies are in the pipeline to deepen this finding.

The mechanism for why the protective effect happens is still TBD, though some hypothesize that detrimental impact of getting Shingles on the brain may cause long term damage that leads to dementia.

Either way, the impacts seem clear, the Shingles vaccine seems like a must-get in a full range defense against dementia.