Older adults who got the shingles vaccine may be at significantly lower risk of developing dementia, a new study in Wales has found.
The study, which was published in the journal Nature, included about 283,000 older adults who were either deemed eligible or not to receive the shingles jab due to a quirk in Welsh vaccine policy.
In 2013, Wales’ government made 79-year-olds eligible for the shingles vaccine, and from then on, people aged into the programme when they turned 79. But due to limited supplies, adults who were 80 or older at the time were never offered the jab.
Researchers from the US, Germany, and Austria homed in on people who turned 80 the week before the vaccine eligibility cutoff and compared them to those who turned 80 the following week.
About half of those who were eligible got the vaccine.
After seven years, about one in eight people who did not get the vaccine had dementia. But those who got the jab were 20 per cent less likely to be diagnosed, the study found.
The effects were much stronger among women than men.
"It was a really striking finding," Dr Pascal Geldsetzer, the study’s senior author and an assistant professor of medicine at Stanford University in the US, said in a statement.
"This huge protective signal was there, any which way you looked at the data".
Other studies have also suggested that the shingles vaccine could help keep dementia at bay.
Last year, an analysis published in Nature Medicine showed that people who got a newer version of the shingles vaccine were at significantly lower risk of developing dementia in the six years after they were immunised.
The two vaccines are made differently. The newer, more common jab contains a protein from the varicella zoster virus, which causes both chickenpox and shingles. The vaccine in the Welsh study used a weakened live version of the virus.
In 2023, the UK phased out the live virus vaccine in favor of the newer jab from the drugmaker GSK because it appears to provide protection from shingles over a longer period of time.
People can develop shingles – a painful rash of fluid-filled blisters that can take weeks to clear up – years after getting chickenpox if the dormant virus is reactivated. Older people and those with weakened immune systems are at higher risk.
Both recent studies were natural experiments that are fairly similar to randomised trials, which are the gold standard for medical research. Because of the eligibility criteria for the shingles jab, the researchers were able to compare two otherwise similar groups of people, allowing them to identify the likely impact of vaccination.
"What makes the study so powerful is that it’s essentially like a randomised 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," Geldsetzer said.
Questions remain to prove causation
The studies indicate that regardless of the type of jab, the shingles vaccine could offer some protection against dementia – though more research is needed to prove it.
It also isn’t clear what’s driving the link. Geldsetzer’s team said viruses that affect the nervous system may raise the risk of dementia, but the theory needs to be tested.
Meanwhile, the disparity between women and men might be explained by differences in their immune systems, given they respond differently to infections and vaccinations, according to Dr Maxime Taquet, a clinical lecturer at Oxford University in the UK who led the 2024 study.
"Even though this remains kind of hypothetical, we think this is playing a part in why we see a difference in men and women," Taquet told Euronews Health.
To help solidify the evidence, the drugmaker GSK said last week that it is studying data from about 1.4 million older adults in the United Kingdom, some of whom got its shingles vaccine and some of whom did not.
Similarly to the Welsh policy change, in 2023, the UK expanded its shingles vaccination programme from adults 70 and older to adults 65 and up – but those aged 66 to 69 at the time were told they had to wait until they were 70 to get the jab.
In another natural experiment, researchers will track whether they develop dementia symptoms.
The recent findings on shingles vaccination could represent a new frontier for Alzheimer’s research, which for decades has struggled to produce breakthroughs in prevention or new treatments.
Alzheimer’s disease is the most common form of dementia, which affects 7 million people in Europe, according to estimates from the European Brain Council.
"Dementia is such a huge burden," Taquet said.
"By triggering the right immune pathways in people, we might be able to reduce or even reverse the dementia process," he added.
"There's many, many steps between where we are now and actually getting there, but I think this is an exciting new lead in this area".
