Older adults who received the shingles vaccine Shingrix had a 24% lower risk of dementia over four years, according to a large new analysis — the latest in a string of studies hinting at a link, though none has proven the vaccine actually prevents dementia.
Researchers led by Brown University analyzed Medicare claims and health records from 509,926 adults aged 66+ admitted to skilled nursing facilities between 2017 and 2022. Only 8,843 had been vaccinated. Using a method called target trial emulation — designed to mimic a randomized trial using real-world data — they estimated the vaccine might prevent roughly one dementia case per 17 people vaccinated. The findings appeared in Annals of Internal Medicine.
Why causation isn’t settled
The authors are explicit that the study cannot establish cause and effect. Vaccinated participants were slightly younger and healthier, and although the researchers adjusted for such differences, those adjustments “did not fully explain the association.” People who choose to get vaccinated often differ in health behaviors that independently affect dementia risk — a classic confounding problem. Confirming a real protective effect would require randomized clinical trials.
Why it matters
Shingrix (a recombinant zoster vaccine introduced in 2017) is the only shingles vaccine on the market, and it’s already recommended for older adults to prevent shingles. If a dementia benefit were confirmed, it would be a remarkable bonus. For now, the practical takeaway is unchanged: the vaccine is worth getting to prevent shingles, and the dementia link is a promising lead, not proof. This article summarizes observational research and is not medical advice.