An analysis of more than 500,000 Medicare beneficiaries suggests that older adults who received the recombinant shingles vaccine had a lower risk of developing dementia than those who didn’t get the shot.
A 24% lower risk among vaccinated residents
Researchers found a 24% relative reduction in dementia risk over four years among vaccinated residents. The relative reduction translates to an absolute risk reduction of about 6 percentage points.
After adjusting for demographic and health factors, the association remained.
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The results aren’t simply because vaccinated people tend to be healthier.
Why shingles vaccination might protect the brain
The exact mechanism isn’t clear, but researchers have several hypotheses.
The most direct one: preventing shingles reduces neuroinflammation and lowers stroke risk — both linked to dementia. “We don’t know with certainty why the risk of dementia is lower with shingles vaccination, but we have a lot of ideas,” the pharmacist said.
Another theory involves the shot’s adjuvants — ingredients that boost immune response.
Some evidence suggests that strong immune activation from certain vaccines might have protective effects beyond the targeted infection. The assistant professor noted that “trials and well-designed observational studies comparing dementia risk between vaccines may be the next step to understand these mechanisms.”
The recombinant shingles vaccine (Shingrix) replaced the older live vaccine Zostavax in 2020. Earlier studies in Wales and Australia had already linked Zostavax to lower risk of the condition. The new analysis extends that finding to the vaccine, which is already recommended for adults 50 and older by the U.S. Centers for Disease Control and Prevention.
Observational study, not proof of cause and effect
The research has important limitations.
It was observational, not a randomized trial. People who got vaccinated were generally younger and healthier than those who didn’t, though the statistical adjustments tried to account for that. Only 8,843 individuals in the overall study group received the shot — a low vaccination rate that highlights ongoing gaps in vaccine uptake among a vulnerable population.
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“A future trial that compares the benefits of shingles vaccination as compared to other vaccinations, as well as usual care or no vaccination, would help to solidify the evidence,” the author said.
The authors acknowledge funding from GlaxoSmithKline.
The company had no control over the study design, analysis, or publication decision. For now, the immunization should still be viewed primarily as protection against herpes zoster. Its potential role in dementia prevention remains an active area of research — one that could reshape how we think about vaccination and brain health in older adults.
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