- Vaccines are increasingly linked to a lower risk of Alzheimer’s disease.
- New research suggests a particular flu vaccine reduces risk by 55%.
- The link is still being explored.
Alzheimer’s disease affects the lives of millions of people around the world. But as common as it is, scientists still don’t entirely know what causes Alzheimer’s, or even the best way to prevent it.
Still, slowly but surely, experts are learning more about this devastating disease. And among the more intriguing avenues of inquiry is a growing body of research tying vaccinations to a lower risk of developing Alzheimer’s.
The latest study in this vein, published in the journal Neurology, makes a strong case for staying up to date on your vaccines. Researchers analyzed data from about 165,000 older adults who received a high-dose flu vaccine or a standard-dose flu vaccine. They discovered that people aged 65 and up who got the high-dose vaccine had a nearly 55% lower risk of developing Alzheimer’s disease over the two-year study period.
Previously, the same research team published two related studies. The first, published in 2022, found that older adults who got the standard-dose flu vaccine had a 40% lower risk of developing Alzheimer’s disease over the four-year study period. The second, published in 2023, found that getting vaccinated against tetanus and diphtheria, with or without pertussis, shingles, or pneumococcus vaccines, was associated with a lower risk for Alzheimer’s disease.
What’s behind this link? Below, doctors break it down.
Meet the experts: Amesh A. Adalja, M.D., an infectious disease specialist and adjunct assistant professor at the Johns Hopkins Bloomberg School of Public Health; C. Buddy Creech, M.D., M.P.H., director of the Vanderbilt Vaccine Research Program; Davide Cappon, Ph.D., director of neuropsychology at Tufts Medical Center.
What is the high-dose flu vaccine?
The high-dose flu vaccine contains four times the antigen—the element that creates an immune response—of the standard-dose flu vaccine, according to the Centers for Disease Control and Prevention (CDC).
The CDC recommends that all adults aged 65 and up get the high-dose vaccine, as data suggest high-dose flu vaccines are more effective than standard ones for older adults. However, if the high-dose flu vaccine isn’t available, the CDC still suggests getting the standard-dose vaccine.
Why might vaccines help to lower the risk of Alzheimer’s disease?
It’s important to stress that the research only found a correlation between getting vaccinated and having a lower risk of Alzheimer’s disease—it didn’t prove that vaccination itself prevented Alzheimer’s in any way.
Still, experts have a few theories about this link. “This is likely related to inflammation that occurs after an influenza case,” says Amesh A. Adalja, M.D., an infectious disease specialist and adjunct assistant professor at the Johns Hopkins Bloomberg School of Public Health. “Inflammation has a role in the development of Alzheimer’s disease, and by blunting the inflammatory effect after viral infections, the influenza vaccine—and others—decreases the risk of Alzheimer’s disease.”
C. Buddy Creech, M.D., M.P.H., director of the Vanderbilt Vaccine Research Program, expresses a similar sentiment. “It is possible that reducing the risk of infections—multiple kinds—can reduce inflammation and cellular damage that could contribute to Alzheimer’s. As we get older, our ability to recover from injury, infection, and inflammation is reduced,” he says. As a result, what may have been simple to treat in early adulthood, like a urinary tract infection, can lead to hospitalization, an altered mental state, and overall health decline in older adults—even after recovery. “Another reason could be non-specific activation of the immune system—not germ-specific—that may change the development of Alzheimer’s,” he says. Additionally, there might be something about reducing the risk of flu itself, rather than the immune effects of getting the flu, that’s driving the drop in Alzheimer’s disease risk.
On the other hand, Dr. Creech says, people who stay on top of their vaccines may simply be healthier overall, which could drive down their risk of developing Alzheimer’s disease.
Basically, there’s a lot more to explore here.
Which flu vaccine should you get?
Doctors recommend getting vaccinated according to the vaccine schedule—again, the CDC recommends the high-dose vaccine for those aged 65 and up—and your healthcare provider’s recommendations.
“Any diminishment of the inflammation will be beneficial,” Dr. Adalja says. “The high dose is a more powerful vaccine, but the low-dose also has a benefit.”
What’s the takeaway?
Experts stress that the link between vaccines and Alzheimer’s disease risk is still being investigated—but it doesn’t hurt to stay on top of your vaccinations. “We simply do not understand yet all of the ways that infections can harm health,” Dr. Creech says. “Studies like this show us that, on the surface, vaccination against common infections, like influenza, can have important effects on our wellbeing.”
Davide Cappon, Ph.D., director of neuropsychology at Tufts Medical Center, stresses that while it’s “reasonable” to think that staying up-to-date on vaccinations contributes to a brain-healthy lifestyle, it’s just one piece of the puzzle. “The strongest evidence still supports managing vascular risk factors, exercising regularly, eating a healthy diet (such as a Mediterranean-style diet), staying socially and cognitively engaged, treating hearing loss and sleep apnea, and addressing depression and anxiety,” he says. “Those interventions likely have a larger impact on long-term brain health than any single intervention.”
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