Routine Vaccines Could Reduce Dementia Risk: The Trained Immunity Hypothesis

A growing body of evidence links routine vaccines-including those for shingles, flu, RSV, and Tdap-to a reduced risk of dementia. Scientists are now proposing a startling mechanism: trained immunity.

Traditional vaccines work by training adaptive immune cells-T cells and B cells-to recognize specific pathogens. However, the innate immune system, once thought to be static, may also be trainable. This concept, known as trained immunity, involves epigenetic changes that allow innate immune cells to respond more aggressively to a broad range of threats.

Researchers led by Justin Devine hypothesize that this trained immunity may counteract the neuroinflammation linked to dementia. By priming the innate immune system to better manage infections, vaccines could prevent the brain inflammation that contributes to cognitive decline.

A recent study found a dose-dependent response: higher doses of the seasonal flu vaccine were associated with lower dementia risk, lending weight to the hypothesis. The shingles vaccine also shows a strong protective link, potentially by preventing reactivation of the varicella-zoster virus in the brain.

While still a hypothesis, the idea could open new avenues for preventing dementia and promoting healthy aging through vaccination.