A growing pile of research is finding a positive correlation between vaccinations and a reduced risk of Alzheimer's disease and related dementias, The Washington Post reported Oct. 26.
Multiple studies have found an association between higher vaccination rates and lower prevalence of Alzheimer's disease, including two studies published in 2023, one in 2022 and another in 2021. Researchers aren't sure why this is happening, according to the Post.
One research team followed nearly 2 million people who were either vaccinated or unvaccinated against the flu. They found that, among the 935,887 people in each group, a yearly flu shot reduced the risk of dementia by 20% over four to eight years.
It's unclear why vaccinations for influenza, pneumococcal pneumonia and other infectious diseases might delay dementia. A few emerging theories are that infectious agents factor into Alzheimer's disease, meaning that vaccines' efficacy could go beyond the intended effect, and that vaccines calm the immune system's reaction to amyloid plaque buildup.