April 16, 2025
Getting vaccinated against shingles may reduce the risk of developing dementia, according to a new report. The study provides some of the strongest evidence to date that the virus that causes shingles, a painful condition caused by the same virus that causes chickenpox, may play a role in the onset of Alzheimer’s disease and other forms of dementia.
Most people are infected with the chickenpox virus, even if they don’t remember having had chickenpox as children, and about a third will eventually get shingles. The virus lies dormant in nerve roots for decades, and as people age and their immune systems weaken, the virus can be reactivated, causing the painful blisters of shingles. Shingles can affect the head, torso or other regions and, in addition to searing pain, lead to vision or hearing loss or potentially fatal brain inflammation. That’s why experts recommend that healthy people aged 50 and older get vaccinated against shingles.
For the current study, researchers took advantage of an unusual public health policy in the United Kingdom that served as a kind of “natural experiment.” When the shingles vaccination program was first introduced in Wales on September 1, 2013, vaccine supplies were very limited, and the vaccine was eligible only to those adults who were 79 on that date; men and women who were 80 or older weren’t eligible to receive the vaccine.
By comparing people who turned 80 just before or just after the vaccine rollout date, researchers were able to compare the two groups — who were similar in most respects, except for their eligibility to get vaccinated against shingles. In essence, the existence of the two groups served as a kind of randomized controlled trial, the gold standard of medical research.
“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,” said Dr. Pascal Geldsetzer, an assistant professor of medicine at Stanford University and senior author of the study.
Over the next seven years, the researchers compared the health outcomes of the two groups. Not surprisingly, those who had been vaccinated were much less likely to have an outbreak of shingles. But by 2020, when the participants were 86 or 87 years old, the researchers found that those who had been vaccinated against shingles were also 20 percent less likely to develop Alzheimer’s disease or another form of dementia. The protective effect was particularly pronounced in women, who are more likely to get shingles than men.
The authors reported similar findings after examining medical records of people in England, which used a similar age-based criteria for administering the vaccine. Nine years after the vaccine rollout, they found dementia listed as the underlying cause of death 20 percent less often in those eligible for vaccination compared to those who were not.
“It was a really striking finding,” Dr. Geldsetzer said. “This huge protective signal was there, any which way you looked at the data.” The study was published in the journal Nature.
The findings bolster results from an earlier study published last year that analyzed medical records from more than 200,000 older Americans. Those results suggested that newer shingles vaccines were associated with even better protection against dementia than the older vaccines.
Scientists aren’t sure why shingles might lead to cognitive decline. The chickenpox virus that causes shingles, varicella zoster, has been linked to an increased risk of heart disease and stroke, both risk factors for dementia. Some research suggests the virus may also damage the lining of blood vessels, including those in the brain, or damage nerve cells directly. Infections may also increase brain inflammation, which may play a role in dementia onset; by limiting the severity of infections, vaccines may reduce brain inflammation.
More research is needed to better understand how viruses such as varicella zoster may contribute to the onset of Alzheimer’s disease. In the meantime, it’s a good idea for all older adults to get vaccinated against shingles. The Centers for Disease Control and Prevention recommends that all Americans 50 and older get two doses of the Shingrix vaccine. The vaccine was approved for use in 2017, replacing an older type of shingles vaccine. It is given in two doses, two to six months apart.
The Shingrix vaccine is highly effective in preventing or limiting damage from a shingles outbreak. And who knows, it could help protect you from Alzheimer’s disease years down the road.
By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Eric Schmidt, PhD, of The Fisher Center lab at The Rockefeller University.
Source: Markus Eyting, Min Xie, Felix Michalik, et al : “A natural experiment on the effect of herpes zoster vaccination on dementia.” Nature, April 2, 2025
