- An analysis of more than 500,000 Medicare beneficiaries highlights that older adults who received the recombinant shingles vaccine (RZV) had a lower risk of developing dementia than those who were not vaccinated.
- Vaccination was associated with a 24% relative reduction in dementia risk over 4 years, equating to an absolute risk reduction of approximately 6 percentage points compared with unvaccinated individuals.
- The protective association persisted after adjusting for a wide range of demographic and health factors, suggesting the findings were not solely explained by differences between vaccinated and unvaccinated groups.
- Although the study adds to growing evidence linking shingles vaccination to lower dementia risk, it does not prove cause and effect.
Research conducted in
As such, researchers wanted to evaluate whether the newer RZV may also provide a protective benefit against dementia in older adults at high risk for the condition who were not up to date with shingles vaccination.
The findings, published in Annals of Internal Medicine alongside a patient summary, note that older adults admitted to skilled nursing facilities in the U.S. who received at least one dose of RZV had a lower likelihood of developing dementia during the following 4 years compared with those who remained unvaccinated.
This analysis adds to growing evidence that the shingles vaccine may offer benefits beyond preventing the painful viral condition, suggesting Shingrix could also be associated with a substantially lower risk of developing dementia.
Researchers from Brown University School of Public Health and collaborating institutions analyzed Medicare claims and electronic health record data from older adults ages 66 years and older admitted to more than 5,500 skilled nursing facilities in the U.S. between 2017 and 2022. Only 8,843 of 509,926 participants received the Shingrix vaccine.
Using a study design known as a ‘target trial emulation,’ the investigators sought to mimic the conditions of a randomized clinical trial as closely as possible using real-world health data.
To be eligible for the study, participants could not have a prior diagnosis of dementia and had to be eligible to receive Shingrix. The team compared residents who received at least one dose of the RZV within 12 months of entering a skilled nursing facility with similar residents who did not receive the vaccine.
Over a 4 year follow-up period, vaccinated individuals experienced a 24% relative reduction in dementia risk and a 6-percentage-point absolute reduction in dementia risk. Only 18.8% of vaccinated adults developed dementia compared with 24.6% of those who were not vaccinated.
“Our findings show that as many as 1 in every 17 dementia diagnoses may be prevented through shingles vaccination,” lead study author Kaley Hayes, PharmD, PhD, an assistant professor at Brown University’s School of Public Health, told Medical News Today.
“We don’t know with certainty why the risk of dementia is lower with shingles vaccination, but we have a lot of ideas. The most obvious factor is through the reduction of shingles infections, which cause neuroinflammation and increase the risk of stroke.”
– Kaley Hayes, PharmD, PhD
The recombinant shingles vaccine is already recommended for
While it is too early to recommend the vaccine specifically for dementia prevention, the new findings add to growing evidence that vaccination could offer broader health benefits than previously recognized.
As researchers continue to investigate the connection, the study provides another reason to explore how preventing infections and supporting immune health may influence long-term brain function.
While the exact biological mechanism remains unclear, one suggestion is that preventing shingles and reducing viral reactivation may help protect the brain from inflammation or other neurological effects associated with the varicella-zoster virus.
Another hypothesis focuses on the vaccine’s immune-stimulating properties. Some research suggests that components known as adjuvants, which enhance immune responses, could play a role in promoting protective effects beyond infection prevention, which could help lower dementia risk.
“There are also emerging hypotheses that vaccination in general, particularly those that result in really robust immune activation, might be the protective mechanism here,” Hayes explained. “Trials and well-designed observational studies comparing dementia risk between vaccines may be the next step to understand these mechanisms.”
“Understanding how we can prevent upstream causes of dementia is key to the future of brain health, as we currently have no preventative treatments.”
“The shingles vaccine may just be one intervention of many that can help to reduce risk, and it’s encouraging to see that something designed to prevent the physical ailment of shingles may also help to keep our brains healthy, too.”
– Kaley Hayes, PharmD, PhD
“A future trial that compares the benefits of shingles vaccination as compared to other vaccinations, as well as usual care or no vaccination, would help to solidify the evidence and better understand whether there is a larger immunologic mechanism by which vaccines preserve brain health, or the effects are through prevention of shingles.”
For now, experts emphasize that shingles vaccination should continue to be viewed primarily as an effective way to reduce the risk of shingles, while its potential role in dementia prevention remains an active area of research.
Although the findings are encouraging, the study does not prove that the shingles vaccine directly prevents dementia.
Because the research was observational, unmeasured differences between vaccinated and unvaccinated individuals may still have influenced the results despite extensive statistical adjustments.
For example, those who got vaccinated tended to be younger and healthier than those who did not, which may have also lowered their dementia risk. However, after adjusting for a wide range of demographic and health-related factors, the association remained.
The study data also notes that vaccination rates among skilled nursing facility residents were relatively low, highlighting an ongoing gap in vaccine uptake among a population at elevated risk for both shingles and dementia.
As such, further trials are still necessary to establish whether shingles vaccination directly reduces dementia risk and to determine the mechanisms involved.
Additionally, the authors acknowledge funding from GlaxoSmithKline, which manufactures Shingrix, noting that the company had no control over the study design, analysis, or decision to publish the results.
