CLEVELAND, Ohio — For those over 65, vaccines for shingles, pneumonia, tetanus, pertussis and diphtheria may offer protection from more than the diseases they were designed to prevent.

According to the authors of a new study, those basic vaccinations come with a surprising side benefit — protection against Alzheimer’s disease.

The study was preliminarily published online the first week of August and will appear in print in the Journal of Alzheimer’s Disease on Sept 12.

Last year, the same group of researchers from the University of Texas Health Science Center at Houston found a similar protective benefit from a regular annual flu shot. Patients who received annual flu shots were 40% less likely to develop Alzheimer’s disease than patients who didn’t get flu shots, the researchers found.

“We don’t usually get to see results like that,” lead author Paul Schulz told the online medical magazine Verywell at the time. Because vaccinations usually create a mild, temporary inflammation in patients, any benefits for a condition like Alzheimer’s came as a complete surprise.

And yet scientists have long suspected that cells of the immune system, particularly those involved in the inflammatory process, play a role in Alzheimer’s.

“When we look under the microscope, we see activated immune cells around every plaque,” Schulz said in the 2022 article.

The results prompted the researchers to ask whether their initial findings were specific to flu vaccines, or if they might occur with other vaccines as well. What they discovered was that prior vaccination against tetanus and diphtheria, shingles and pneumonia are all associated with a substantial reduced risk for developing the neurodegenerative disease.

Patients who received the Tdap/Td vaccine for tetanus, diphtheria and whooping cough were 30% less likely than their unvaccinated peers to develop Alzheimer’s disease (7.2% of vaccinated patients versus 10.2% of unvaccinated patients developed the disease).

Similarly, HZ vaccination for shingles, or herpes zoster, was associated with a 25% reduced risk of developing Alzheimer’s disease (8.1% versus 10.7%).

For the pneumonia vaccine, there was an associated 27% reduced risk of developing the disease (7.9% versus 10.9%).

When comparing the absolute risk - the difference between 7.2% to 10.2 % might not sound like much, but that represents a 30% relative risk reduction.

To put these results into context, three new antibody-based anti-amyloid drugs used to treat Alzheimer’s have shown they slow disease progression at the same rate as vaccines, which are, better studied, more easily administered and significantly less expensive.

Dr. Paul E. Schulz, at UTHealth Houston, was senior author of a study that found several vaccinations were linked to a reduced risk of Alzheimer's disease.UTHealth Houston

It’s still unclear exactly how the vaccines are protecting the brain, but researchers, including Schulz and his team think that they may boost the effectiveness of immune cells that are already attempting to repair the damage done by toxic buildup of beta-amyloid proteins in the brain, or by decreasing overall inflammation.

“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,” said Schulz, who is also a professor of neurology with McGovern Medical School at UTHealth Houston.

The study was performed by comparing the health and vaccination data from large medical databases, and the authors say it underscores the value that these large datasets of health information play in research, as well as the importance of routine vaccinations to overall health.

“Our findings are a win for both Alzheimer’s disease prevention research and for public health in general, as this is one more study demonstrating the value of vaccination,” said study co-author Kristofer Harris.

Alzheimer’s disease affects more than 6 million people living in the U.S., with the number of affected individuals growing due to the nation’s aging population.