Zoster vaccine reduced the probability of a new dementia diagnosis by approximately one-fifth over a seven-year follow-up period.
https://www.nature.com/articles/s41586-025-08800-x
A natural experiment on the effect of herpes zoster vaccination on dementia - Nature

Using a natural experiment that avoids common bias concerns, this study finds that the live-attenuated shingles vaccine reduced the probability of a new dementia diagnosis within a follow-up period of 7 years by approximately one-fifth.

Nature