Zoster Vaccine Reduces Dementia Risk by 20 Percent: Nature Study Finds

Although neurotropic herpesviruses have been increasingly implicated in the pathogenesis of various dementias, previous research has relied heavily on associational data that are frequently compromised by unmeasured confounding factors like patient motivation or health literacy. Consequently, a significant clinical gap remains regarding the vaccine's causal impact, prompting Dr Pascal Geldsetzer and colleagues from the Stanford University School of Medicine to initiate this study to determine whether the herpes zoster vaccination could effectively prevent or delay the onset of dementia using a robust natural experiment

Therefore, the quasi-experimental study employed a regression discontinuity design utilizing the Secure Anonymised Information Linkage (SAIL) Databank in Wales, which encompasses electronic health records (EHR) for 282,541 adults born between 1925 and 1942. Over a seven-year follow-up period, the researchers compared the incidence of the primary endpoint, new dementia diagnoses, between individuals who were eligible for the vaccination based on an exact birth date cut-off of 2 September 1933, and those who were ineligible; the analysis specifically excluded 13,783 participants with pre-existing dementia to ensure the results reflected new clinical events.

Key Clinical Findings of the Study Include:

• Significant Risk Mitigation: The study demonstrated that immunization led to a 3.5 percentage point absolute reduction in new dementia cases, which corresponds to preventing approximately one in five expected diagnoses

• Marked Sex Disparity: Healthcare providers should observe that the protective benefits were substantially greater among women, who experienced a 5.6 percentage point reduction, while the effect in men was not statistically significant

• Concurrent Shingles Protection: Reaffirming the vaccine’s established efficacy, the data showed a relative 18.8% reduction in the probability of patients experiencing at least one shingles episode during the follow-up

• High Diagnostic Specificity: The investigation confirmed that the vaccination’s impact was uniquely focused on shingles and dementia, as the study found no influence on other common causes of mortality or major chronic conditions

• Durable Long-term Effects: Evidence suggests that the reduction in dementia incidence began to emerge roughly one year after vaccination and remained consistent throughout the seven-year observation window.

The results suggest that the live-attenuated zoster vaccine reduced the probability of a new dementia diagnosis by approximately one-fifth over a seven-year follow-up period. This robust protective effect suggests that the immunization may play a critical role in altering the trajectory of neurodegenerative disease in older populations.

These findings indicate that clinicians might consider the herpes zoster vaccine a potentially far more effective and cost-efficient intervention for delaying the onset of dementia than currently available pharmaceutical options.

While the study's conclusions are limited by potential diagnostic under-detection and a focus on a specific age cohort near 80 years, there is a clear need for future research to confirm these findings in broader populations and to further explore the underlying immunomodulatory mechanisms.

Reference

Eyting, M., Xie, M., Michalik, F., Heß, S., Chung, S., & Geldsetzer, P. (2025). A natural experiment on the effect of herpes zoster vaccination on dementia. Nat