Reduced Risk of Dementia Linked to Eight Vaccines

According to multiple large observational studies, the risk of dementia is associated with eight routine adult vaccines: the shingles, respiratory syncytial virus, influenza, DTP (diphtheria, tetanus and pertussis), pneumococcal, hepatitis A, hepatitis B and typhoid vaccines.

A 2024 study found the recombinant shingles vaccine Shingrix was associated with a significantly lower risk of dementia than the older live vaccine Zostavax, which has since been discontinued in the U.S. And a follow-up study in 2025 found an 18 percent reduction in dementia diagnoses over 18 months in more than 436,000 people who received the shingles vaccine.

That same follow-up study found a 29 percent reduction in dementia risk over 18 months in those who received the RSV vaccine, Arexvy.

A 2022 study that analyzed nearly two million people aged 65 and older found those who received at least one flu vaccine were 40 percent less likely to develop Alzheimer’s over four years. And, the more frequently people were vaccinated, the greater the protection.In April 2026, the same researchers found a high-dose flu vaccine, which contains four times the antigen of the standard jab, was linked to a 55 percent reduced risk.

A 2023 study found adults aged 65 and over who received the tetanus, diphtheria and pertussis (Tdap) or Td (without pertussis) vaccine were 30 percent less likely to develop Alzheimer’s over an eight-year follow-up. Another meta-analysis that pooled data from 17 studies and more than 1.8 million people showed the risk of developing dementia was reduced by 31 percent. And, a more recent meta-analysis in 2025 of 104 million participants found a 33 percent reduction.

The same meta-analysis found a 27 percent reduced risk of Alzheimer’s in adults who had received the pneumococcal vaccine. And, a 2025 meta-analysis that pooled data from 21 studies covering 104 million participants also found a significant association.

A systematic review from the University of Cambridge in January 2025 that analyed 14 studies of health records from approximately 130 million people found vaccinations against hepatitis A, typhoid and the combined hepatitis A and typhoid vaccine were all associated with a lower risk of dementia. And, another study found that receiving both the typhoid and hepatitis A vaccines together was associated with a greater reduction in risk than either vaccine on its own.

The same meta-analysis of the DTP vaccine found hepatitis B vaccination resulted in an 18 percent lower risk of dementia.

And, lastly, a study found typhoid vaccination was linked to a 20 percent reduced risk of dementia.

The researchers offer several theories about why these vaccines are associated with a lower risk of dementia. However, the most straighforward is that vaccines prevent infections, and infections cause inflammation that can damage the brain.