Shingles is nasty, but researchers find a side benefit to getting vaccinated
Receiving the recombinant zoster vaccine (RZV), which prevents herpes zoster (HZ), commonly known as shingles, within a year of entering or leaving a US nursing home dramatically lowers the risk of a dementia diagnosis for up to four years.
The study, published yesterday in
the Annals of Internal Medicine, reinforces past observational
research suggesting the same.
While previous research found that the live attenuated HZ
vaccine reduced the likelihood of a dementia diagnosis, the researchers in this
study wondered if RZV provided the same benefit. The paper found that receiving
a dose of RZV was associated with a 5.8-percentage-point lower risk of a
dementia diagnosis for up to four years.
“[That] translates to about one in 17 dementia cases
potentially being prevented through vaccination,” lead author Kaley Hayes,
PharmD, PhD, associate director of pharmacoepidemiology at the Brown University
School of Public Health, told CIDRAP News. “We were honestly taken aback by the
results. However, they actually are consistent with other studies that have
primarily included the older form of the vaccine.”
An understudied population
For this study, Hayes and colleagues used a target emulation
trial using the Medicare and electronic health records of people aged 66 or
older admitted to nursing homes from January 2017 through December 2022. This
allowed researchers to mimic a randomized controlled trial.
They posed the question, Would receiving an RZV dose within
a year of an acute health event impact dementia risk?
The study included 509,926 people in 5,550 skilled nursing
facilities and examined their medical records for up to four years after
discharge. The researchers excluded people who died or previously had a
dementia diagnosis. Of that remaining group, 8,843 (1.73%) had received at
least one RZV dose within a year of discharge, with 87% being vaccinated after
leaving the facility. The other 259,518 did not receive the vaccine.
In the four years after vaccination, RZV recipients were at a 24% lower risk of dementia than unvaccinated participants (relative risk, 5.8 percentage points).
Hayes said they looked at people in nursing homes because
they wanted to understand if high-risk participants also would experience
benefits. “This population [is] really understudied, completely excluded from
trials and also not even included in a lot of real world studies,” she
said.
Hayes said they addressed the healthy vaccinee bias—the idea
that people who receive vaccines are in better health—to single out the
vaccine’s effect on dementia diagnoses. The biggest difference between the
groups is that some people who received RZV had previously received the live
attenuated vaccine.
“In terms of things that might affect the dementia risk, we
did see some differences in their history,” she said. “Overall, the vaccinated
group seemed a little bit healthier.” They were also slightly younger than
their peers who did not receive RZV.
There are some limitations to the study. Real-life data
differ from data collected in a randomized controlled trial, said Hayes. They
also didn’t have a “good definition of a new dementia diagnosis.” They examined
factors such as doctors’ visits and new prescriptions for dementia medications
as proxies for such a diagnosis.
“I would say that no real-world data capture of an outcome
like dementia, which is so complicated, is perfect,” Hayes said. “It is a
limitation.”
Potential role of reduced shingles-related strokes
A 2025 study found
that people who received the live-attenuated HZ vaccine had a 20% lower risk of
being diagnosed with dementia over the next seven years. Researchers are trying
to understand the relationship between shingles vaccination and lower dementia
risk. For now, they have theories.
“It’s probably multifactorial,” Hayes said. “When you think
of a shingles case, there may be higher risks of strokes.” Protecting people
from strokes and similar events likely reduces their chance of developing
dementia, she said.
Researchers have also thought that the shingles vaccine
might reduce an accumulation of amyloid plaques and neurofibrillary tangles,
Hayes said. “There’s a little bit less evidence for that.”
Hayes believes that a randomized controlled trial is the
natural next step for examining shingles vaccination and dementia risk. “It
really is time for a trial to get this squared away,” she said.
