High-dose flu shot may lower risk of Alzheimer's

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May 14, 2026

By Maureen Salamon, Executive Editor, Harvard Women's Health Watch

Reviewed by Robert H. Shmerling, MD, Senior Faculty Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing

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A vial of flu vaccine on a white surface next to a syringe with the cap removed.

Getting a flu shot might do more than just protect you from infection: a higher-dose flu vaccine may reduce older adults' risk of developing Alzheimer's disease over the next several years compared with a standard dose, according to a study published April 28, 2026, in Neurology.

Researchers analyzed US insurance claims data from more than 164,000 people ages 65 and older (56% women). Nearly 121,000 had received a high-dose flu shot, while about 44,000 got a standard-dose flu vaccine. Participants were followed for up to three years after vaccination, and the researchers estimated how many developed Alzheimer's by tracking diagnosis codes and prescriptions for Alzheimer's medications.

The high-dose vaccine was linked to a slightly lower risk of developing Alzheimer's in the handful of years after vaccination; researchers estimated that the higher dose prevented one case of the disease for every 185 people vaccinated. The benefit also appeared stronger in women. The study was observational, meaning it couldn't prove that higher-dose flu shots prevented Alzheimer's - only that an association exists. Also, the three-year follow-up period in this study is a short window for assessing the development of dementia, the study authors noted.

Image: © Peter Dazeley/Getty Images

About the Author

Maureen Salamon, Executive Editor, Harvard Women's Health Watch

Maureen Salamon is the executive editor of Harvard Women’s Health Watch. She also writes for the Harvard Health Letter, Harvard Heart Letter, and Harvard Men’s Health Watch, as well as for Harvard Health Publishing’s flagship website. … See Full Bio

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About the Reviewer

Robert H. Shmerling, MD, Senior Faculty Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing

Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School. … See Full Bio

View all posts by Robert H. Shmerling, MD

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