Can Vaccinations Save Your Brain?

It’s also possible that vaccines may enhance the ability of the immune system to remove amyloid plaques. Schulz was the senior author of a recent study that found a statistically significant difference in the incidence of Alzheimer’s after following two groups — one vaccinated against the flu, the other unvaccinated — for up to eight years.

The groups, of 935,887 each, were obtained from a national patient database. To ensure a valid comparison, both groups shared many of the same characteristics and risk factors, including age, gender and conditions such as hypertension, Schulz says — except one group was vaccinated and the other was not.

He and his colleagues found that patients who received at least one flu vaccine during the follow-up period of four years were 40 percent less likely to develop Alzheimer’s compared with those who did not get the vaccine. Additional analysis found that those who received an annual flu shot had the lowest rate of the disease.

“The more vaccinations you got, the better,” Schulz says.

His team has been studying the effects of vaccines for other infectious diseases, including shingles, pneumococcal pneumonia and the combination of tetanus, diphtheria and pertussis (whooping cough), known as Tdap, with similar findings, he says.

Another recent study, still to be peer-reviewed, concluded that vaccination with Zostavax (the early shingles vaccine) among a quite senior population in Wales averted an estimated 1 in 5 new dementia diagnoses during a seven-year period, according to Pascal Geldsetzer, M.D., assistant professor of medicine at Stanford University, who conducted the research.

“The exact size of the preventive effect of shingles vaccination for dementia is hard to pinpoint in such an analysis, but our study suggests that the effect is substantial,” Geldsetzer says. “We believe that our analysis provides compelling evidence that shingles vaccination prevents or delays dementia in this older age group.”

Virologist Robert T. Schooley, M.D., an infectious disease specialist at the University of California, San Diego — who has not been involved in any of the studies — says it is “certainly plausible” that reducing the frequency and severity of influenza through vaccination can quell immune activation over time.

“Other conditions associated with chronic or recurrent uncontrolled systemic inflammation such as chronic HIV infection can also be associated with accelerated cognitive decline, and this mechanism might well account for the findings,” he says.

Though experts say the growing evidence is promising, some suggest caution when interpreting the results.

“No matter how hard you try to control that the two groups are comparable, there is the residual sense that folks who choose to get vaccinated are different in unmeasurable ways from those who do not get vaccinated,” says William Schaffner, M.D., professor of preventive medicine at Vanderbilt University School of Medicine. These “unmeasured differences” could have an impact on the incidence of dementia and distort the possible influence of the vaccines, he says.

Regardless, Schaffner adds, “this is not an issue that ought to figure notably in one’s decision whether to receive vaccines. The data are clear that vaccines help prevent influenza, COVID, pneumococcal disease, shingles and so forth. As I am wont to observe: Disease bad; vaccines good.”

Schooley agrees, saying, “One thing is for certain: Whether or not this observation is real, staying up to date with vaccinations for influenza and other infectious diseases as we age is a good idea.”