A LIVE-attenuated herpes zoster vaccine may help reduce the risk of developing dementia, according to a new study that used a natural experiment to provide stronger causal evidence than previous observational research.
Researchers took advantage of a unique eligibility cut-off based on exact date of birth: individuals born on or after 2 September 1933 were eligible to receive the zoster vaccine for at least 1 year, while those born just 1 week earlier were permanently ineligible. This created two closely matched groups that differed significantly only in their likelihood of being vaccinated. The study analysed large-scale electronic health records and employed a regression discontinuity design to assess the impact of vaccination on subsequent dementia diagnoses.
Findings showed a striking 47.2% vaccination rate among those born just after the eligibility date, compared to only 0.01% among those born just before it. Over a seven-year follow-up period, individuals who received the zoster vaccine had a 3.5 percentage point lower probability of receiving a new dementia diagnosis (95% CI: 0.6–7.1, P=0.019), corresponding to a 20% relative reduction in risk (95% CI: 6.5–33.4). The protective effect was more pronounced in women than in men. These results were independently validated using mortality data from both England and Wales, showing similar reductions in dementia-related deaths among vaccinated individuals.
This study offers compelling evidence that zoster vaccination may delay or prevent dementia onset, with a design that minimises common biases found in correlational studies. Further research is needed to explore the underlying mechanisms and whether similar benefits extend to other vaccines.
Reference
Eyting M et al. A natural experiment on the effect of herpes zoster vaccination on dementia. Nature. 2025; DOI: 10.1038/s41586-025-08800-x.
