# Recombinant zoster vaccine is associated with a reduced risk of dementia

## TL;DR

A study found that getting two doses of the recombinant zoster vaccine is linked to a 51% lower risk of dementia in older adults.

## Contribution

This study provides new evidence that the recombinant zoster vaccine significantly reduces dementia risk in older adults.

## Key findings

- Two doses of RZV were associated with a 51% lower risk of dementia.
- The risk reduction was consistent across age and racial/ethnic groups.
- The association remained significant after adjusting for healthy vaccinee bias.

## Abstract

Vaccines to prevent herpes zoster have been associated with reduced dementia risk. We conducted a retrospective matched cohort study of Kaiser Permanente Southern California members aged ≥65 years who received two doses of RZV 4 weeks–6 months apart between 01 April 2018 and 31 December 2020, with no dementia diagnoses or dementia medications prior to or within 6 months of their second RZV dose. Cox regression with inverse probability of treatment weighting was used to estimate adjusted hazard ratios (aHRs). The study included 65,800 RZV-vaccinated individuals and 263,200 unvaccinated matches. Vaccination with two doses of RZV was associated with a 51% lower risk of dementia (aHR: 0.49 [95% confidence interval (CI): 0.46–0.51]); aHRs were comparable across age, and racial and ethnic groups, but the risk reduction was stronger in females compared to males. In an evaluation of potential healthy vaccinee bias, the aHR of dementia for RZV compared to Tdap was 0.73 (95% CI: 0.67–0.79). Vaccination with two doses of RZV is associated with a statistically significant reduction in the risk of dementia in adults aged ≥65 years. After accounting for healthy vaccinee bias, RZV vaccination remains associated with a statistically significant lower risk of dementia.

The study shows that vaccination with two doses of recombinant zoster vaccine is associated with a 51% reduction in the risk of dementia in adults aged ≥65 years. Reduction in risk is comparable across subgroups and remains statistically significant after accounting for healthy vaccinee bias.