Shingles vaccine may actually slow down dementia, study finds

A common vaccine meant to ward off shingles may be doing something even more extraordinary: protecting the brain.

Earlier this year, researchers reported that the shingles vaccine cuts the risk of developing dementia by 20 percent over a seven-year period.

A large follow-up study has found that shingles vaccination may protect against risks at different stages of dementia — including for people already diagnosed.

The research, published Tuesday in the journal Cell, found that cognitively healthy people who received the vaccine were less likely to develop mild cognitive impairment, an early symptomatic phase before dementia.

Crucially, the study suggests that the shingles vaccine — two doses of which are recommended for adults 50 and older or those 19 and older with a weakened immune system — may help people who already have dementia. Those who got the vaccine were almost 30 percent less likely to die of dementia over nine years, suggesting the vaccine may be slowing the progression of the neurodegenerative syndrome.

“It appears to be protective along the spectrum or the trajectory of the disease,” said Anupam Jena, a professor of health care policy at Harvard Medical School and a physician at Massachusetts General Hospital who reviewed the paper.

There are few effective treatments for dementia and no preventive measures outside lifestyle changes.

The results have led to cautious excitement among researchers.

If these findings are confirmed, “then this would be groundbreaking for dementia,” said Maxime Taquet, an associate professor at Oxford University who has conducted research into shingles vaccination and dementia risk. “I think there’s no other word for it.”

Research has linked common vaccines, including for shingles, to lower dementia risk.

For these observational studies, there is a “healthy vaccine bias,” said Ascherio, who wasn’t involved in the study. “People who get vaccines tend to be healthier in general than people who don’t” because they may have different health-related behaviors.

Because randomized controlled trials — the gold standard in medical research — aren’t often feasible in the real world, scientists who conducted the research published Tuesday took advantage of a historical quirk in how Wales rolled out its shingles vaccination program in 2013.

“The question then is: Where do you start with this vaccine during the disease course? And does it have benefits for those who already have the condition?” said Pascal Geldsetzer, an assistant professor of medicine at the Stanford University School of Medicine and a senior author of the research.

The vaccine was not only associated with a 20 percent reduction of dementia diagnoses, but also a 3.1 percent reduction in diagnoses of mild cognitive impairment over nine years.

“It suggests that from a clinical public health perspective, we should be providing this potentially at early stages, maybe on a regular basis,” Geldsetzer said.

There doesn’t seem to be a time when it’s too late in the disease progression to derive benefits, he added.

Dementia, in its final stages, can lead to death.

“Bad dementia can lead you to aspirate and have respiratory arrest,” said Jena, who wasn’t involved in the study. “Bad dementia can lead you to be unable to care for yourself.”

The shingles vaccine decreased deaths due to dementia by 29.5 percent. Even when looking at all-cause mortality, the shingles vaccine was associated with a 22.7 percent reduction.

These results “suggest that there is a slowing of this degenerative process,” which seems to be “striking good luck that the vaccine designed for something else would slow a degenerative process,” Ascherio said.

The magnitude of the effects is “almost too good to be true,” said Taquet, who wasn’t involved in the study.

“If those effect sizes really pan out in randomized control trials, then this would be perhaps one of the best treatments we’ve had for dementia in a while, which is the reason why we need to be quite cautious with interpretation,” he said. “That’s why we need the randomized control trials, but I think they really provide the strongest possible push for randomized control trials.”

For one, the study looked at the older shingles vaccine using a weakened version of the live varicella-zoster herpes virus. That vaccine has been discontinued in the United States, as well as in the European Union and Australia, and has been replaced with the Shingrix vaccine, which is more effective at preventing shingles and may also be associated with a lower risk of dementia.

However, it’s unknown whether the newer vaccine is also associated with a reduced risk for mild cognitive impairment or death due to dementia, researchers said. Despite its strengths, and its being as close to a randomized controlled trial without being one, the study is still correlational and cannot get at causation.

Still, experts unanimously encourage eligible people to get the vaccine, which reduces the reactivation of the varicella-zoster virus. The virus causes chicken pox in childhood and remains dormant in neuron clusters within the spinal cord. When reactivated in adulthood, the varicella-zoster virus manifests as shingles, which is characterized by a burning, painful rash and can sometimes cause lifelong chronic pain conditions or serious complications in a subset of people.

The Centers for Disease Control and Prevention recommends two doses of a shingles vaccine for adults 50 and older or those 19 and older with a weakened immune system. But uptake has been relatively low: In 2022, 34.4 percent of eligible Americans, including those with weakened immune systems, had received at least one dose of a shingles vaccine in their lifetime.

In the meantime, researchers are pushing for randomized controlled trials as well as studies to understand why the vaccine is protective, which can teach us something fundamental about dementia and help develop better treatments.

Geldsetzer is working to raise money for a randomized controlled trial to directly test the older shingles vaccine on dementia risk, which he said should require less investment because it’s known to be safe and have other benefits.

There’s a lot of excitement to work on this from other researchers, he said, but he’s had no luck getting the money.