New Shingles Vaccine Linked to Lower Dementia Risk in Older Adults, Study Finds

A large new analysis of Medicare data suggests that older adults who received the modern shingles vaccine were significantly less likely to develop dementia than those who did not get the shot.

Researchers examined health records from 1.5 million Medicare beneficiaries aged 65 and older. They found that people who received two doses of the recombinant shingles vaccine—sold under the brand name Shingrix—had a 33% lower risk of developing any type of dementia over a follow-up period of three years or less.

The study, published in the journal *Alzheimer’s & Dementia*, compared two groups: 502,845 older adults who received both doses of the shingles vaccine and 1,005,690 similar individuals who were not vaccinated. The groups were matched by age, sex, and race or ethnicity.

Among those who got the vaccine, the rate of new dementia cases was 10.45 per 1,000 person-years. In the unvaccinated group, that rate was 15.73 per 1,000 person-years. A person-year is a measurement that accounts for both the number of people in a study and how long they were followed.

The protective effect held across different types of dementia. Over three years or less, vaccinated individuals had a 28% lower risk of Alzheimer’s disease and a 33% lower risk of vascular dementia compared with those who did not get the vaccine.

When researchers looked at longer follow-up periods—more than three years—the benefits remained, though they were slightly smaller. Over that time, the risk of any dementia was 26% lower, the risk of Alzheimer’s was 17% lower, and the risk of vascular dementia was 34% lower among vaccinated individuals.

Dr. Susan dos Reis of the University of Maryland School of Pharmacy, the lead author, noted that this is one of the first studies to test the two-dose recombinant shingles vaccine in a large, representative group of Medicare beneficiaries using a comparison group from the same time period.

“The findings support the growing evidence from real-world data showing that the herpes zoster vaccine is associated with a lower risk of new-onset dementia,” dos Reis said. She added that the team ran several rigorous checks on their data and that the results held up.

The researchers pointed out that many earlier studies on shingles vaccines and dementia looked at an older type of shot—the live-attenuated zoster vaccine, sold as Zostavax—which is no longer available in the United States.

Recent research from Wales and Canada has shown that the live shingles vaccine also lowered dementia risk. And in 2024, a study found that people who mostly received the newer recombinant vaccine went 17% longer without a dementia diagnosis compared with those who got the live version.

Dr. Maxime Taquet of the University of Oxford, who was not involved in the Medicare study, said the population-based evidence suggests that shingles vaccination might delay or prevent dementia. But he stressed that more work is needed.

“The two most important steps toward understanding whether the vaccine has a protective effect are clinical trials to confirm the causal effect, and mechanistic studies to understand why the recombinant shingles vaccine may protect against dementia,” Taquet said.

To reduce bias, the researchers designed the study carefully. They compared vaccinated people to unvaccinated people who had a routine preventive care visit around the same time. This helped account for the fact that people who get vaccines may generally be healthier.

All participants were at least 65 years old at the time of their second vaccine dose or preventive care visit. They had been enrolled in Medicare Parts A, B, and D for at least 11 months and had no history of dementia. People in Medicare Advantage plans were not included.

In both the vaccinated and unvaccinated groups, 60% of participants were women, 93% were white, and 55% were between ages 70 and 79. Dementia diagnoses were identified using Medicare claims data. The researchers adjusted for medical conditions, prescription drug use, healthcare visits, and other vaccinations.

The results remained strong even after the researchers accounted for factors such as how long it might take for dementia to develop and whether people had previously received tetanus, diphtheria, and pertussis (Tdap) or live shingles vaccines.

The study had some limitations. Dementia diagnoses may have been recorded incorrectly in some cases. Also, the researchers could not measure certain factors that might influence dementia risk, such as a person’s education level, marital status, or how physically active they were.

The authors noted that infections like shingles might increase the risk of dementia, but the evidence on this point has been mixed.

“Despite the accumulating real-world evidence, further work is needed to evaluate if there is a causal association between recombinant zoster vaccine and reduced risk of dementia,” dos Reis said.

Source: MedPage Today