A live-attenuated shingles vaccine, commonly administered to older adults to prevent herpes zoster, may have an unexpected benefit: a significantly reduced risk of developing dementia. New findings from researchers at Stanford Medicine show that individuals who received the vaccine were 20% less likely to be diagnosed with dementia over a seven-year period. This reduction surpasses that of any other known prevention method for dementia to date.
The study leveraged a unique natural experiment in Wales, where vaccine eligibility was sharply determined by date of birth. People born just one week after the September 2, 1933 cutoff had a 47.2% vaccination rate, compared to only 0.01% for those born one week prior. This sharp contrast between two otherwise nearly identical groups allowed researchers to apply a regression discontinuity design to draw stronger causal inferences than typical observational studies allow.
What makes this more than a statistical anomaly is the replication of similar findings across several countries, including England, Australia, New Zealand, and Canada. The research team is now preparing a large randomized controlled trial to further test the hypothesis that herpes zoster vaccination can delay or prevent dementia onset.
The study supports a growing body of evidence suggesting that neurotropic viruses—those that affect the nervous system—may play a role in triggering or accelerating dementia. If viral load or chronic inflammation are contributing factors, then vaccination might serve as an indirect yet effective form of neuroprotection. The effect appeared to be stronger in women than in men, though the mechanisms behind that sex difference remain unclear.
As noted in the coverage, the study’s findings could shift the narrative around dementia prevention away from expensive therapeutics and toward scalable public health strategies already in place. While the results are promising, especially for aging populations, they arrive at a time when public funding for such research is under threat, following deep cuts to the National Institutes of Health.
For now, the shingles vaccine stands not just as a guard against painful rashes, but possibly as a surprising ally in the long-term preservation of cognitive health.