Older individuals who received the shingles vaccine had a significantly reduced risk of developing dementia later in life, according to a new study that researchers are calling “remarkable.” The study, which examined the health records of older adults in Wales, found that those who received the shingles vaccine were 20% less likely to develop dementia over the following seven years than those who did not. These findings not only reinforce the connection between certain viral infections and cognitive decline but also hint at the possibility that a widely available intervention may help slow the progression of one of the world’s most devastating neurological conditions.
The shingles virus, also known as herpes zoster, is caused by the varicella-zoster virus—the same virus that causes chickenpox. After a person recovers from chickenpox, usually during childhood, the virus remains dormant in the body’s nerve cells. As people age or as their immune systems weaken, the virus can reactivate, resulting in shingles, which manifests as a painful, blistering rash. Though shingles itself is not fatal, it can lead to complications like chronic nerve pain, and—according to this new research—may also be linked to the onset of dementia.
“The findings support an emerging theory that infections which affect the nervous system, like shingles, may increase the risk of neurodegenerative diseases,” explained Dr. Pascal Geldsetzer, senior author of the study and researcher at Stanford Medicine. “Our research indicates that preventing these viral reactivations might also reduce the risk of cognitive decline.”
Previous observational studies had hinted at this connection, but many suffered from a major source of bias: individuals who choose to get vaccinated are often more health-conscious and likely to engage in other behaviors that protect against dementia. Such confounding factors made it difficult to determine whether the vaccine itself was protective, or whether those who got vaccinated were already at lower risk due to healthier lifestyles.
Recognizing this problem, Dr. Geldsetzer identified a unique opportunity in Wales to reduce the bias: a natural experiment created by the country’s phased rollout of the shingles vaccine. In 2013, Wales began offering the vaccine to people who were exactly 79 years old, limiting the supply by age. That seemingly arbitrary cutoff created two similar populations—those who were 79 and received the vaccine, and those who had just turned 80 and missed the opportunity.
“We know that if you take a thousand people born in one week and compare them to a thousand people born the following week, there should be no systematic differences between the groups,” Geldsetzer said. “So this age-based policy created a situation that mimics the gold standard of a randomized controlled trial.”
Leveraging this approach, the Stanford team analyzed the anonymized health records of over 280,000 older adults who did not have dementia at the start of the program. They narrowed the focus to people closest to the age cutoff—those who turned 80 just before the rollout and those who turned 80 just after—essentially forming a control and intervention group.
Fast-forward seven years to 2020, and the results were compelling. One in eight of the Welsh seniors had been diagnosed with dementia. However, those who received the shingles vaccine were 20% less likely to be among them.
“It was a really striking finding,” said Geldsetzer. “This huge protective signal was there, any which way you looked at the data.”
Importantly, the team also tested the data for other possible explanations, such as socioeconomic status, pre-existing health conditions, or differing rates of other vaccinations, and found no significant differences. “Because of the unique way in which the vaccine was rolled out, bias in the analysis is much less likely than would usually be the case,” he said. “The signal in our data was so strong, so clear, and so persistent.”
Interestingly, the study, published in the journal Nature, revealed another compelling detail: the protective effect of the vaccine appeared to be more pronounced in women. While the study did not definitively explain this difference, Geldsetzer offered some possibilities. “Women tend to mount stronger immune responses to vaccines than men, and they’re also more likely to develop shingles in the first place,” he noted. “Those two factors could explain why the vaccine appears to offer greater protection for women.”
To determine whether these findings were specific to Wales or more universally applicable, Geldsetzer’s team examined health records from countries with similar shingles vaccination rollouts, including England, Canada, Australia, and New Zealand. “We just keep seeing this strong protective signal for dementia in dataset after dataset,” he said.
Despite the robustness of the findings, Geldsetzer stressed the need for a large-scale clinical trial to more definitively establish causation. Such a trial would address lingering questions and test whether the vaccine directly protects against dementia or does so indirectly by preventing the virus from causing neurological inflammation.
“This would be a very simple, pragmatic trial,” he explained. “We’re talking about a one-time, proven-safe vaccine that’s already used in clinical practice. There’s minimal risk and potentially enormous benefit.”
One logistical challenge, however, is that the specific shingles vaccine used during the Welsh rollout—a live-attenuated version—has since been phased out and replaced with newer, recombinant alternatives. Still, Geldsetzer believes a trial using the updated version would be worthwhile, especially given its strong safety profile and the growing urgency to find effective dementia prevention strategies.
The implications of this study are profound. As global populations age and dementia becomes an increasingly pressing public health concern, identifying low-cost, scalable interventions is critical. If a commonly available vaccine like the shingles jab can reduce the risk of dementia, it could be a game-changer in how we approach prevention.
“At this point, we need to start thinking differently about dementia prevention,” Geldsetzer emphasized. “It may not be just about brain health—it could also be about managing chronic infections and how our immune systems respond to them.”
As research continues, this unexpected link between a shingles vaccine and reduced dementia risk offers a hopeful glimpse into a future where a single shot in older age could help preserve memory and cognitive function for years to come.
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