A surprising new discovery suggests that a vaccine originally designed to protect older adults from shingles may also help protect their brains. A large study led by Stanford University found that older people in Wales who received the shingles vaccine were about 20% less likely to develop dementia over the following seven years than those who didn’t get the vaccine.
The study, published in Nature, offers the strongest evidence yet that preventing certain viral infections may reduce the risk of dementia.
It supports a growing theory: viruses that lie dormant in the nervous system might play a role in developing conditions like Alzheimer’s disease. If this link proves real, we may already have a useful tool to reduce dementia risk—without needing to wait for a new drug or treatment.
Shingles is caused by the same virus that causes chickenpox—varicella-zoster. After a person recovers from chickenpox, the virus stays hidden in the body’s nerve cells.
In some people, especially older adults or those with weak immune systems, the virus can wake up again and cause shingles, a painful rash. The virus doesn’t just cause skin problems—it can also affect the brain and nerves.
Dementia, including Alzheimer’s disease, affects over 55 million people worldwide. Despite decades of research, there are still no treatments that can prevent or cure it. Most research has focused on proteins called plaques and tangles that build up in the brain, but progress has been slow. Now, scientists are exploring new ideas, including the possible role of viruses.
Previous studies had hinted that people who got the shingles vaccine might also be less likely to get dementia. But there was a problem: people who choose to get vaccinated are often more health-conscious overall. They may eat better, exercise more, and go to the doctor regularly. Those healthy habits could explain their lower risk—not the vaccine itself.
But this new study took advantage of a rare situation in Wales. In 2013, the country rolled out the shingles vaccine in a very specific way. People who turned 79 by September 1 of that year were eligible for a free shot.
Those who turned 80 just before that date were not. Because these rules were based strictly on date of birth, the researchers could compare people who were nearly the same age—but only some of whom were allowed to get the vaccine.
The researchers looked at health records from over 280,000 older adults who did not have dementia at the start. They focused on people born just before and just after the September 1 cutoff. These two groups were nearly identical in terms of age, health, education, and lifestyle—except that one group had access to the vaccine and the other didn’t.
About half of the people eligible for the vaccine chose to get it. Over the next seven years, the researchers found that vaccinated people were 20% less likely to be diagnosed with dementia. They also had a 37% lower chance of getting shingles—just as expected from clinical trials of the vaccine.
The most striking finding was how consistent the data was. The researchers checked for other possible causes—like other diseases or differences in medical care—but found none. The only major difference was in dementia rates. They even re-analyzed the data in several different ways, and the results held up each time.
The protection was stronger in women than in men, which is especially interesting because women are more likely to get shingles and tend to have stronger immune responses to vaccines. This could suggest that the body’s immune reaction plays a role in reducing dementia risk.
Exactly how the vaccine helps prevent dementia is still unknown. It might strengthen the immune system overall, or it might stop the virus from reactivating in the brain. Either way, the results are exciting.
Even more encouraging, similar findings have been seen in other countries, including England, Canada, Australia, and New Zealand. Each time, researchers found the same pattern: lower rates of dementia among people who received the shingles vaccine.
The vaccine used in the study was a live-attenuated version, meaning it contained a weakened form of the virus. This version is no longer being manufactured, but there is a newer shingles vaccine that uses only part of the virus and is even more effective.
Researchers hope to study whether the newer vaccine has the same protective effect against dementia—or maybe an even stronger one.
Dr. Pascal Geldsetzer, the lead researcher, is now pushing for a full randomized controlled trial, the gold standard in science. In such a study, participants would be randomly assigned to receive the vaccine or a placebo shot, allowing researchers to confirm whether the vaccine truly causes a reduction in dementia risk.
The trial would be relatively easy and fast to run, since the vaccine is already proven to be safe and the protective effects may appear within just a couple of years.
In the meantime, these findings offer hope. If confirmed, a widely available vaccine could turn out to be a simple and effective tool to reduce the burden of one of the world’s most devastating diseases.
If you care about dementia, please read studies that eating apples and tea could keep dementia at bay, and Olive oil: a daily dose for better brain health.
For more health information, please see recent studies what you eat together may affect your dementia risk, and time-restricted eating: a simple way to fight aging and cancer.
The research findings can be found in Nature.
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