Do Flu Shots Increase the Risk of Alzheimer's?

If you ask around or search online, you’ll notice some very strong opinions on vaccinations and immunizations. These can range anywhere from people adamantly opposed to receiving any immunizations on one end, to research studies that tout the effectiveness of disease prevention through vaccines. An additional question some people have is how immunizations, specifically the flu shot since it’s offered every year, affect their chances of developing Alzheimer’s.

A patient receiving a shot
MUSTAFA OZER / AFP Creative / Getty Images

What Are Flu Shots?

Flu shots are an immunization available on a yearly basis designed to protect the body against influenza. A common misunderstanding is that they protect against the stomach flu, but rather, they target the upper-respiratory symptoms of influenza including congestion, fever, and cough that can develop into pneumonia and other breathing difficulties.

Each year, the formula of the flu shot is adjusted to try to target the particular strains of influenza that are prevalent at that time. The effectiveness of the flu shot varies, based on how well the vaccine matches up against the actual virus.

Do Flu Shots Cause Alzheimer’s?

You may have heard someone say that they’re not getting a flu shot because it might cause or increase the risk for Alzheimer’s. Are they onto something, or is this a myth?

This idea may come from Dr. Hugh Fudenberg, whose medical license was revoked in 1995. Some internet sites credit him as the source who states that the flu shot increases the risk of Alzheimer's. However, there has been no peer-reviewed research whatsoever that supports this claim.

According to the Alzheimer’s Association, the idea that flu shots (or the chemicals within the shots) cause or increase the risk of developing Alzheimer’s disease is a common myth and is false.

Some flu shots contain a small amount of mercury in the thimerosal, the preservative that may be in some of the flu vaccinations. (Single dose flu shots generally don’t contain this preservative since they’re designed for a one time use when opened.) According to the Centers for Disease Control and Prevention, research consistently demonstrates that the amount of mercury in thimerosal is safe and does not pose any harm, other than minor redness or swelling where you receive the shot.

What Does Research Say?

A research study conducted in 2001 with 4392 participants showed that the risk of developing Alzheimer’s was decreased for those who had received influenza immunizations (flu shots), as well as with for those who received the vaccinations for diphtheria​ or tetanus (grouped together in their research) or poliomyelitis (polio).

This research did not prove that the influenza vaccination was what caused a lower risk of Alzheimer’s, but it did demonstrate that people who received the flu shot were less likely to develop Alzheimer’s and that those who did not receive the vaccination were more likely to develop Alzheimer’s disease.

One other study involving nearly 12,000 people with chronic kidney disease found that those who received the influenza vaccine had a significant reduction in the development of dementia. 

If My Loved One Has Dementia, Should I Consent to a Flu Shot for Her?

Research suggests that the immune response of older adults with dementia is weaker than in cognitively normal adults, so a flu shot may give a needed boost to her immunity. Additional research reports that 1.5 times as many people with dementia die from influenza compared to the national average.

A Word From Verywell

Although there are some who raise strong concerns about flu shots and other immunizations, the fact remains that any side effects from immunizations are closely monitored, and vaccines have been credited with saving many, many lives. At this time, research does not support any concern about the flu vaccine being tied to an increase in dementia risk. Rather, the flu shot often helps protect older adults from serious illnesses and complications that can result from influenza. 

Of course, before you make a health care decision, you should discuss the risks and benefits with your physician.

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  2. Centers for Disease Control and Prevention. Thimerosal in vaccines. Updated October 27, 2015.

  3. Verreault, R, Laurin, D, Lindsay, J, De Serres, G. Past exposure to vaccines and subsequent risk of Alzheimer’s disease. CMAJ 2001;165(11):1495-8.

  4. Liu JC, Hsu YP, Kao PF, et al. Influenza vaccination reduces dementia risk in chronic kidney disease patients: a population-based cohort studyMedicine (Baltimore). 2016;95(9):e2868. doi:10.1097/MD.0000000000002868

  5. Naumova EN, Parisi SM, Castronovo D, Pandita M, Wenger J, Minihan P. Pneumonia and influenza hospitalizations in elderly people with dementia. J Am Geriatr Soc. 2009;57(12):2192-9. doi:10.1111/j.1532-5415.2009.02565.x

  6. Centers for Disease Control and Prevention. People 65 years and older & influenza. Updated November 21, 2019.

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