HOUSTON — You don’t have to look very far to hear all about supposedly negative side-effects tied to various vaccines. Now, researchers from UTHealth Houston are flipping the script. Their report reveals that the flu vaccine may offer a very attractive side-effect — protection against dementia.
The study finds individuals who received at least one influenza vaccine were 40 percent less likely than non-vaccinated people to develop Alzheimer’s disease over the course of a four-year span. To reach this finding, researchers compared Alzheimer’s risk among patients vaccinated against the flu and those who had not. A large, nationwide group of Americans older than 65 took part in the study.
“We found that flu vaccination in older adults reduces the risk of developing Alzheimer’s disease for several years. The strength of this protective effect increased with the number of years that a person received an annual flu vaccine – in other words, the rate of developing Alzheimer’s was lowest among those who consistently received the flu vaccine every year,” says first author Avram S. Bukhbinder, MD, a recent alumnus of McGovern Medical School at UTHealth Houston, in a university release. “Future research should assess whether flu vaccination is also associated with the rate of symptom progression in patients who already have Alzheimer’s dementia.”
What’s in the shot that blocks Alzheimer’s?
This work is actually a continuation of earlier research by UTHealth Houston researchers from 2020 that noted a possible link between the flu vaccine and a lower Alzheimer’s risk. This time around, study authors used a much larger dataset encompassing 935,887 flu-vaccinated patients and 935,887 non-vaccinated patients.
Then, over the next four years, roughly 5.1 percent of the vaccinated participants went on to develop Alzheimer’s. In comparison, 8.5 percent of the non-vaccinated patients also developed Alzheimer’s.
While study authors say it’s clear that there is some type of protective effect coming from the flu vaccine related to dementia, they can’t explain what is happening here without conducting further research.
“Since there is evidence that several vaccines may protect from Alzheimer’s disease, we are thinking that it isn’t a specific effect of the flu vaccine,” adds senior author Paul E. Schulz, MD, the Rick McCord Professor in Neurology at McGovern Medical School. “Instead, we believe that the immune system is complex, and some alterations, such as pneumonia, may activate it in a way that makes Alzheimer’s disease worse. But other things that activate the immune system may do so in a different way — one that protects from Alzheimer’s disease. Clearly, we have more to learn about how the immune system worsens or improves outcomes in this disease.”
The flu vaccine isn’t the first to display potential dementia-fighting benefits. Prior research has linked multiple other vaccines (like tetanus and polio) to decreased risk of dementia. Study authors speculate if future findings will suggest the COVID-19 vaccines hold similar associations.
The study is published in the Journal of Alzheimer’s Disease.