Vaccines May Reduce Alzheimer's Risk By Up To 40%

Getting vaccinated against the flu may reduce your risk of developing Alzheimer’s disease in the future, according to new research.

The research, which was presented at the Alzheimer’s Association International Conference on July 27, is the result of an as-yet-unpublished study that investigated the health records of 9,066 people over the age of 60. After analyzing the data, researchers discovered that people who had one flu vaccine had a 17% lower risk of developing Alzheimer’s disease. But people who were vaccinated more than once over time had an additional 13% lowered risk of developing the disease.

People who had the lowest risk of developing Alzheimer’s disease received their first flu vaccine at a younger age. 

“Our study suggests that flu vaccination may be helpful to prevent Alzheimer’s disease, but further confirmation and actual clinical testing is needed to show this concretely,” study co-author Albert Amran, a fourth-year medical student with McGovern Medical School at The University of Texas Health Science Center at Houston, tells Verywell.

How Can the Flu Shot Lower Your Risk of Alzheimer’s Disease?

There are a few theories.

“Chief among [these theories] is the idea that regular vaccination itself may keep the immune system in shape as the body gets older,” Amran says. “We can see with the ongoing pandemic that response to viruses in older patients is much less controlled and overall poorer.”

Previous research published in the journal Brain, Behavior, and Immunity found that people who have had the flu do not have an increased risk of developing Alzheimer’s disease.

“That suggests to me that there might be something about the flu itself that may be playing a role here,” Amran says. “Both the flu virus and the vaccine contain proteins found in the virus and may be doing something to the immune system to help it prevent Alzheimer’s disease.”

It’s also possible that people who get their flu vaccine are more likely to take better care of their health—and that may lower their risk of Alzheimer’s disease, Lealani Mae Acosta, MD, MPH, a board-certified neurologist specializing in neurodegenerative memory disorders at Vanderbilt University Medical Center who did not work on the study, tells Verywell.

“Often, people who are seeing the doctor regularly and actively trying to optimize their health are the ones more likely to get a flu shot, so it may be that having a healthier lifestyle is the underlying reason,” she says. “We know multiple risk factors, particularly vascular risk factors like high blood pressure and diabetes, are associated with an increased risk of developing Alzheimer's disease, so people who are doing their best to stay healthy with preventative activities like getting the flu shot may also be better at controlling other risk factors for Alzheimer's disease."

It’s important to note that while the study found an association between a lowered risk of developing Alzheimer’s disease and getting a flu shot, the researchers didn’t prove that getting vaccinated against the flu actually lowered a person’s risk. Instead, it’s possible that people who get their flu shot may be more likely to do something else that lowers their Alzheimer’s risk.

“People getting regular flu shots may be taking care of themselves more than those that aren’t," he says, echoing Acosta. "Maybe the behaviors associated with getting annual flu vaccinations may also cause someone to manage their diabetes or heart health risk factors more.”

But, Amran says, his research team controlled for this “as best as we could” by matching patients’ drug histories—including a lot of medications that are usually given during surgery or hospital stays—as a proxy for their use of medical services. “Sicker” vaccinated patients were compared with equally “sick” unvaccinated patients instead of mixing the whole group together.

“With the controls we used in mind, it’s very possible that what we’re seeing may actually be related to the vaccination itself as opposed to the behaviors or medical habits of the patients involved,” Amran says.

Overall, though, “it is hard to say the flu shot directly preserves brain tissue,” Amit Sachdev, MD, director of the Division of Neuromuscular Medicine at Michigan State University, tells Verywell.

Getting Vaccinated Against Pneumonia May Lower Alzheimer’s Risk, Too

Another study presented at the Alzheimer’s Association International Conference found a lowered risk of developing Alzheimer’s and getting the pneumococcal vaccine. That study analyzed data from 5,146 participants from the Cardiovascular Health Study, a population-based, longitudinal study of coronary heart disease and stroke in adults aged 65 years and older.

After analyzing the data, the researchers discovered that getting vaccinated against pneumonia between the ages of 65 and 75 reduced a person’s Alzheimer’s risk by up to 40%. The people with the largest reduction in risk were vaccinated and didn’t carry a specific genetic risk factor for developing the disease.

This particular study also found that people who received the pneumococcal vaccine and flu shot had a lower risk of developing Alzheimer’s.

The same reasons a person might have a lowered risk of developing Alzheimer’s disease after getting a flu shot likely apply to the pneumococcal vaccine as well, Acosta says.

While these new studies don’t draw definitive conclusions, experts say they offer clear guidance.

“The takeaway should be that people of all ages should follow medical guidelines and their doctor's recommendations about getting vaccinated for the flu and pneumonia, as appropriate, not only as a good preventative health measure from these serious infections, but also because it may decrease risk of Alzheimer's disease,” Acosta says.

Sachdev agrees. “Better health overall means better brain health,” he says. “Take care of your body and it will take care of your brain.”