“I was like, ‘Oh my God; that’s totally unexpected.’”The team began researching the relationship between receiving a flu vaccine and Alzheimer’s disease risk.
Recent studies show an association between receiving the recombinant shingles and flu vaccines and a lower risk of Alzheimer’s disease and other types of dementia.
Would the high-dose flu vaccines that many adults 65 and older receive also offer the same benefit?
In this study, the researchers compared people who received a standard-dose flu vaccine to those who received a high-dose flu vaccine.
Schultz and his colleagues are using mouse models to try to understand the mechanisms behind why a high-dose flu vaccine contributes to a lower risk of Alzheimer’s disease.
About seven years ago, Paul Schultz, MD, a professor and neurologist at UTHealth Houston, met with the biomedical informatics team he regularly collaborates with as they investigate risk factors for Alzheimer’s disease. Someone made a comment that piqued his interest.
“My colleagues who were looking through the databases said, ‘Hey, we found a signal that the influenza vaccine seems to be associated with less Alzheimer’s. Is that something you know already?’” Schultz told CIDRAP News. “I was like, ‘Oh my God; that’s totally unexpected.’”
The team began researching the relationship between receiving a flu vaccine and Alzheimer’s disease risk. Their first paper compared people who received the regular flu vaccine with those who didn’t and estimated the likelihood of each group to develop Alzheimer’s.
“Three years of receiving the influenza vaccine was associated with a 20% reduced risk, and six years was associated with a 40% reduced risk of Alzheimer’s for at least eight years,” Schultz explained. “It’s an association, not a cause and effect, but quite striking.”
Over the past several years, more research has emerged showing a relationship between some adult vaccines and a lower risk of dementia. Recent studies show an association between receiving the recombinant shingles and flu vaccines and a lower risk of Alzheimer’s disease and other types of dementia.
“The vaccines themselves are different. But why are they starting to show some signals that they might be reducing risk of dementia or Alzheimer’s disease?” asked Glen Finney, MD, director of the Memory and Cognition Program at Geisinger Health and a fellow of the American Academy of Neurology. “Well, what are vaccines doing? They’re re-training your immune system.”
High- vs standard-dose flu vaccine performance
In their first paper, Schultz and his colleagues compared people 65 years or older who received a flu vaccine to those who did not. “It was actually protective,” he said. “We spent a lot of time trying to verify that to the extent that we could.”
But then another question arose. Would the high-dose flu vaccines that many adults 65 and older receive also offer the same benefit? In this study, the researchers compared people who received a standard-dose flu vaccine to those who received a high-dose flu vaccine. That helped them control for what’s known as at the healthy vaccinee bias: People who regularly receive vaccines tend to be healthier overall than those who do not.
“The high dose did better than the standard dose by like 15%. So it wasn’t a huge amount, but it was measurable,” Schultz explained. “It turns out that the anti-dementia effects last a couple of years. In the paper, we showed that that it’s about two years plus that the anti-dementia effects last—even though the anti-flu effect only lasts four to six months.”
Women, who develop Alzheimer’s disease twice as often as men, experienced a greater benefit from vaccination than men, too. “In women, the high dose was much more effective than the standard dose,” he said. “That’s a really interesting finding.”
The papers describe an association—not a causal relationship. Schultz and his colleagues are using mouse models to try to understand the mechanisms behind why a high-dose flu vaccine contributes to a lower risk of Alzheimer’s disease.
