A new study reveals that a single shingles shot can not only reduce your chances of developing dementia but also benefit those who already have dementia. The revelation comes off the back of a unique vaccine rollout in Wales.
The study, led by Pascal Geldsetzer, assistant professor of medicine at Stanford University, analysed the health records of more than 280,000 adults aged 71 to 88 who were dementia-free at the start of a shingles vaccination programme in Wales, which kicked in on 1 September 2013. Geldsetzer and his team concluded that the likelihood of dementia diagnosis was 20% lower compared to those who didn’t receive a shingles jab.
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Two key findings arose from the research, the first being the underlying mechanisms that link dementia and vaccines. “There’s a growing body of research that shows viruses that preferentially target your nervous system and hibernate in your nervous system for much of your life may be implicated in the development of dementia,” Geldsetzer tells us. “One such virus is the chickenpox virus, which can cause shingles later in life.
“The second mechanism is potentially independent of the chickenpox virus. Specifically, there’s increasing evidence that reveals vaccines can have effects on the immune system that are greater than simply eliciting the specific antibody response for which they have been designed, and that these broader immunological effects can have benefits for other diseases.”
This isn’t the first study to show such an outcome. However, importantly it is the first study to overcome a major limitation in earlier research linking vaccination to reduced dementia risk. Previous analyses using electronic health records compared people who chose to be vaccinated with those who didn’t. These groups could well differ in many ways, such as diet, exercise or other health behaviours. As a result, it’s unclear whether those findings reflected true cause and effect or simply correlations driven by healthier people being more likely to have a vaccine.
“Our study uses a design that closely mimics a randomised controlled trial, the gold standard for establishing causality,” says Geldsetzer. How is random in itself. “When Wales introduced the shingles vaccine in 2013, eligibility depended on whether a person turned 80 shortly before or shortly after the programme start date. Those with birthdays just before the cut-off were permanently ineligible, while those with birthdays just after were eligible for at least a year.
“This created two groups that should be virtually identical except for vaccine eligibility. In our data, even a one-week difference around this cut-off produced a dramatic shift from almost no-one being vaccinated to roughly half being vaccinated, mirroring random assignment.
“Another important aspect of our research is that we see the same protective effect from shingles vaccination for dementia in dataset after dataset, in different populations and different countries that rolled out the vaccine in a similar way as Wales did.”
Interestingly, the protective effect proved greater in women than men. Why, says Geldsetzer, could be due to sex differences in the immune response or in the way in which dementia develops. “Women on average have higher antibody responses to vaccination, for example,” he adds. “We also know that both shingles and dementia are more common in women than in men.”
If the shingles vaccine really prevents or delays dementia, and also benefits those who already have dementia, it’d clearly be a hugely important finding for society. “But what we really need to convince the public health and medical community is a clinical trial,” says Geldsetzer. “I’m trying to raise funds to conduct such a trial via private and philanthropic foundations.
" We want to trial the live-attenuated vaccine – which is the vaccine for which we have generated our compelling body of evidence – and that is off-patent. So, if there is anyone out there who might be interested in helping to fund such a trial to definitively test if shingles vaccination prevents or delays dementia, it’d be great if they could get in touch with me at pgeldsetzer@stanford.edu.”
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