Certain adult vaccines, including shingles and pneumonia shots, may also help seniors fight off Alzheimer's disease, new research reveals.

Prior vaccination with the shingles vaccine, pneumococcus vaccine or the tetanus and diphtheria shot, with or without an added pertussis vaccine, are associated with a 25% to 30% reduced risk of Alzheimer's disease, according to researchers from the University of Texas Health Science Center at Houston.

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This study follows one published last year in which the researchers found that adults who received at least one flu shot were 40% less likely than their unvaccinated peers to develop Alzheimer's disease.

"We were wondering whether the influenza finding was specific to the flu vaccine. This data revealed that several additional adult vaccines were also associated with a reduction in the risk of Alzheimer's," said senior author Dr. Paul Schulz, a neurology professor with McGovern Medical School at UTHealth Houston.

"We and others hypothesize that the immune system is responsible for causing brain cell dysfunction in Alzheimer's. The findings suggest to us that vaccination is having a more general effect on the immune system that is reducing the risk for developing Alzheimer's," Schulz added in a University of Texas news release.

For the study, the researchers evaluated medical records of 1.6 million patients who did or did not receive routine vaccinations recommended in adulthood. Patients were free of dementia during a two-year lookback period and were at least 65 years old by the start of the eight-year follow-up period.

Folks who received the Tdap/Td vaccine to protect against tetanus and diphtheria were 30% less likely than their unvaccinated peers to develop Alzheimer's disease, according to the research. About 7% of vaccinated patients developed Alzheimer's versus 10% of unvaccinated patients.

Shingles vaccination was associated with a 25% reduced risk of developing Alzheimer's disease (8% of vaccinated patients versus 11% of unvaccinated patients). The pneumococcal vaccine was associated with a 27% lower risk of developing the disease (8% of vaccinated patients versus 11% of unvaccinated patients).

In comparison, three new anti-amyloid antibodies used to treat Alzheimer's slow disease progression by 25%, 27%, and 35%, the study team noted.

"We hypothesize that the reduced risk of Alzheimer's disease associated with vaccines is likely due to a combination of mechanisms," said study author Dr. Avram Bukhbinder, a recent medical school alumnus now at Massachusetts General Hospital, in Boston.

"Vaccines may change how the immune system responds to the build-up of toxic proteins that contribute to Alzheimer's disease, such as by enhancing the efficiency of immune cells at clearing the toxic proteins or by 'honing' the immune response to these proteins so that 'collateral damage' to nearby healthy brain cells is decreased," he said. "Of course, these vaccines protect against infections like shingles, which can contribute to neuroinflammation."

The research highlights how important it is for patients to have ready access to routine adult vaccinations, the researchers noted.

The study findings were published online recently in theJournal of Alzheimer's Disease.