A study of more than 500,000 older adults found that people who received at least one dose of the recombinant shingles vaccine had a lower rate of dementia diagnoses over the next four years.
The researchers looked at 509,926 Medicare beneficiaries who had recently stayed in a skilled-nursing facility. Dementia was diagnosed in 18.8 percent of vaccinated participants, compared with 24.6 percent of those who were not vaccinated.
The team used a method called target trial emulation to make the comparison more useful, and checked the results in several ways. The association remained, but it was smaller after additional checks for possible bias.
The study was observational, so it cannot show that the vaccine itself caused the lower risk. Clinical trials and further research will be needed to understand whether the protection is real and why it might occur.
