As we get older, we face an increased risk of both dementia and shingles – but what if a single vaccine could provide protection against them both?
There's already convincing evidence that an older shingles vaccine, developed under the brand name Zostavax, can protect against dementia.
A new and improved shingles vaccine, with the brand name Shingrix, has been less extensively studied – something that researchers led by a team from Brown University in the US wanted to address.
In their new study, researchers analyzed patient data for 509,926 people admitted to nursing facilities between January 2017 and December 2022.
Picking this group of people meant having a natural health 'checkpoint' that can be used for reference, among those already at a higher risk of both dementia and shingles.
The data showed that over a four-year follow-up period, 18.8 percent of study participants who got a Shingrix vaccine shot within 12 months of admission developed dementia, compared to 24.6 percent of those who didn't get the vaccine.
That amounts to a 24 percent reduction, which is pretty remarkable.
"This study looks at the newest vaccine only in an older, vulnerable adult population who were not up to date with shingles vaccination and are at a very clear clinical point in care: entering a skilled nursing facility," says pharmacoepidemiologist Kaley Hayes from Brown University.
"It fits into this large puzzle that's just starting to come together that the vaccines are effective at preventing shingles and also appear to have neuroprotective benefits as well."
Shingrix has now replaced Zostavax for shingles vaccination in many parts of the world: It's more effective, and it lasts longer.
We're also now seeing that it can reduce dementia risk, and this new work isn't the first study to make the connection.
The advantages of this new study are the relatively large sample size, the real-world setting, and the targeting of people particularly vulnerable to shingles and dementia due to their age and need for nursing care.
Uptake for the Shingrix vaccine was relatively low during the study period – just 8,843 out of the 509,926 participants got a vaccine shot – and the researchers hope the 24 percent risk reduction could convince more people to get the protection.
"This translates to about one in 17 dementia cases potentially being prevented," says Hayes.
There are some limitations to the study. As it's an observational analysis, we can't say for sure that there's direct cause and effect here, and there may be some 'vaccine bias' at play (meaning healthier people at lower risk for dementia anyway may be more likely to get a vaccine).
It's also not yet clear why this association exists – but that's something that future studies can dig into.
"We don't know with certainty why the risk of dementia is lower with shingles vaccination, but we have a lot of ideas," Hayes told Judy George at MedPage Today.
"The most obvious factor is through the reduction of shingles infections, which cause neuroinflammation and increase the risk of stroke.
"There are also emerging hypotheses that vaccination in general, particularly those that have really robust immune activation, might be the protective mechanism here."
It's also worth noting that the study was funded by GlaxoSmithKline, which manufactures Shingrix. The researchers state that GlaxoSmithKline had no control over the study design, the data analysis, or the decision to publish the results.
Given the matches with previous studies, and the historical links between shingles vaccines and dementia risk, there's good reason to believe that Shingrix is carrying on the good work of Zostavax in this regard.
With the Centers for Disease Control and Prevention (CDC) recommending shingles vaccinations for adults over 50 in the US, the researchers suggest checking into nursing facilities could also be a time to check if people want to get vaccinated.
Related: Positive Thinking May Help You Get More Out of Your Vaccines
"Our cognition is so tied to our overall health and what happens to us physically," says Hayes.
"It's really amazing to see that something that's supposed to prevent a physical ailment can also help keep our brain healthy, too."
The research has been published in Annals of Internal Medicine.