Study: Flu Shots May Reduce the Risk of Alzheimer's Disease

What Is the High-Dose Flu Shot? , Vaccine
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Key Takeaways

  • A large study suggested that being vaccinated against the flu may reduce the risk of developing Alzheimer’s disease by 40% in a four-year period following the shot.
  • Smaller studies have found similar results and other vaccines have been associated with a lower risk of dementia.

Getting your flu shot might have additional benefits. According to a recent study, influenza vaccination was associated with a 40% decrease in the four-year risk of developing Alzheimer's disease.

In a study conducted two years ago, the same team of researchers found a similar connection between the flu shot and a 17% reduced risk of Alzheimer's. The latest study involved a very large sample size of nearly 2 million U.S. adults aged 65 and older.

The 40% risk reduction was surprising, according to Paul Schulz, MD, a co-author of the study and director of the Neurocognitive Disorders Center at McGovern Medical School at the University of Texas Health Science Center at Houston.

“We don’t usually get to see results like that,” Schulz told Verywell. Since vaccinations usually create a mild, temporary inflammation in patients, he did not expect the flu shot to have additional benefits for a condition like Alzheimer's.

The Study

Researchers analyzed data collected from September 2009 to September 2019, which included anonymous information on medical claims from people 65 and older. The patients had no diagnosis of dementia, mild cognitive impairment, or encephalopathy at the beginning of the study.

During the follow-up period of nearly four years, around 5% of people who had received a flu shot developed Alzheimer’s disease compared with 8.5% of people who had not been vaccinated.

In the past few years, scientists have recognized that immune cells might play a role in the progression of Alzheimer's. “When we look under the microscope, we see activated immune cells around every plaque," Schulz said.

The influenza vaccine may be selectively affecting the part of the immune system that is related to Alzheimer’s, he explained. But it is too early to tell whether getting the flu shot alone can reduce the risk of developing this neurodegenerative disorder.

Heather M. Snyder, PhD, vice president of medical and scientific relations at the Alzheimer’s Association, said "more research is needed to understand the biological mechanisms behind the results in this study."

“For example, it is possible that people who are getting vaccinated also take better care of their health in other ways, and these things add up to lower risk of Alzheimer’s and other dementias," Snyder said.

Other Vaccines May Help, Too

Other vaccines may also help reduce the risk of developing Alzheimer’s, Schulz said. Adult vaccines, such as the ones against tetanus, shingles, and tuberculosis, have been associated with a lower risk of dementia.

People who received the flu shot more than once had an even lower risk of developing Alzheimer’s, as multiple vaccines may have strengthened the effect, Schulz added.

Health authorities have encouraged flu vaccinations for decades as they have a known safety profile. Even if further research fails to confirm the association between flu vaccination and risk reduction for Alzheimer's, Schulz said, people should still be getting their flu shot annually.

What This Means For You

Getting vaccinated against the flu appears to reduce the risk of developing Alzheimer’s disease by 40% in a four-year period following the shot. Several other vaccines have been linked to a reduction in the risk of dementia too.

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Bukhbinder AS, Ling Y, Hasan O, et al. Risk of Alzheimer’s disease following influenza vaccination: A claims-based cohort study using propensity score matching. Kostev K, ed. JAD. Published online June 13, 2022:1-14. doi:10.3233/JAD-220361

  2. Amran A, Lin Y, Kim Y, Bernstam E, Jiang X, Schulz PE. Influenza vaccination is associated with a reduced incidence of Alzheimer’s disease: Epidemiology / Risk and protective factors in MCI and dementiaAlzheimer’s and Dementia. 2020;16(S10). doi:10.1002/alz.041693

  3. Heneka MT. An immune-cell signature marks the brain in Alzheimer’s diseaseNature. 2020;577(7790):322-323. doi:10.1038/d41586-019-03892-8

  4. Klinger D, Hill BL, Barda N, et al. Bladder cancer immunotherapy by bcg is associated with a significantly reduced risk of Alzheimer’s disease and Parkinson’s diseaseVaccines. 2021;9(5):491. doi:10.3390/vaccines9050491

  5. Scherrer JF, Salas J, Wiemken TL, Jacobs C, Morley JE, Hoft DF. Lower risk for dementia following adult tetanus, diphtheria, and pertussis (Tdap) vaccination. Lipsitz L, ed. The Journals of Gerontology: Series A. 2021;76(8):1436-1443. 10.1093/gerona/glab115

  6. Lehrer S, Rheinstein PH. Herpes zoster vaccination reduces risk of dementiaIn Vivo. 2021;35(6):3271-3275. doi:10.21873/invivo.12622

By Valerie DeBenedette
Valerie DeBenedette has over 30 years' experience writing about health and medicine. She is the former managing editor of Drug Topics magazine.