• Posted April 2, 2025

Shingles Vaccine Protects Against Dementia

The shingles vaccine can do more than protect seniors from painful, blistering rashes.

It also appears to protect older folks from dementia, researchers say.

Seniors who got the shingles vaccine when it became available in the U.K. were 20% less likely to develop dementia than those who did not take the jab, according to research published April 2 in the journal Nature.

“It was a really striking finding,” senior researcher Dr. Pascal Geldsetzer, an assistant professor of medicine at Stanford University, said in a news release. “This huge protective signal was there, any which way you looked at the data.”

These findings came about due to a “natural experiment” that resulted from the way the shingles vaccine was handed out in Wales after it became available in 2013, Geldsetzer said.

Shingles is caused by the same virus that causes chicken pox, varicella-zoster. The virus stays dormant in the nerve cells of people who get chicken pox as children, and then re-emerges as folks’ immune systems weaken due to old age or illness.

The vaccine works by boosting seniors’ immune response against varicella-zoster, preventing the dormant virus from emerging and causing shingles.

However, researchers wondered if the shingles vaccine might protect the brain as well. Recent evidence has indicated that certain viral infections might increase a person’s risk of dementia.

To test this theory, researchers looked to Wales. There, on Sept. 1, 2013, public health officials began offering the vaccine to anyone 79 years of age.

People could only get the vaccine once they’d turned 79, and only for that year. Once folks turned 80, they were out of luck, including anyone who’d already turned 80 by the start of the vaccine program.

The rules were designed to ration a limited supply of vaccine, but they also created a natural randomized trial that could test the vaccine’s effects on people, researchers said.

By comparing people who turned 80 just before September 2013 with those who turned 80 just after, researchers could isolate the vaccine’s effects.

“We know that if you take a thousand people at random born in one week and a thousand people at random born a week later, there shouldn’t be anything different about them on average. They are similar to each other apart from this tiny difference in age,” Geldsetzer said.

“What makes the study so powerful is that it’s essentially like a randomized trial with a control group — those a little bit too old to be eligible for the vaccine — and an intervention group — those just young enough to be eligible,” he added.

Researchers tracked health outcomes over the next seven years for people who got the vaccine versus those who didn’t.

As expected, shingles cases were 37% lower in people who’d received the vaccine, researchers found.

But by 2020, vaccine recipients also were 20% less likely to develop dementia, results show.

This finding held even after researchers considered other potential factors that might influence dementia risk like level of education or chronic illnesses such as diabetes, heart disease or cancer.

“The signal in our data was so strong, so clear and so persistent,” Geldsetzer said.

Results also showed that the protection against dementia was much more pronounced in women than in men.

This could be because women on average respond better to vaccination than men, researchers said. Also, shingles is more common in women than in men, so the vaccine’s protection might matter more for them.

This research team has since replicated the Wales findings using health records from England, Australia, New Zealand and Canada.

“We just keep seeing this strong protective signal for dementia in dataset after dataset,” Geldsetzer said.

It’s not clear, however, why the vaccine would protect against dementia at all, researchers said.

It might protect the brain by boosting the immune system overall, or by specifically preventing varicella-zoster from having some yet-unknown affect on brain health, researchers speculated.

It’s also not known whether the newest version of the vaccine, which is the only one available in the U.S., would confer the same protection, researchers noted.

The first vaccine, Zostavax, contained a live but weakened version of the varicella-zoster virus to which the immune system responded.

It’s now been replaced by Shingrix, a genetically engineered version of the vaccine that contains only certain proteins from the virus.

Shingrix is more effective against varicella-zoster – 97% versus 51% in clinical trials – but might have a different impact on dementia risk than its predecessor, researchers said.

Geldsetzer hopes these new findings will inspire others to look into Shingrix’s effectiveness against dementia.

“At least investing a subset of our resources into investigating these pathways could lead to breakthroughs in terms of treatment and prevention,” he concluded.

More information

The U.S. Centers for Disease Control and Prevention has more on shingles.

SOURCE: Stanford University, news release, April 2, 2025