Could the shingles vaccine protect against dementia? What the evidence says.
Dementia is one of the greatest fears for the over 60s, and despite years of dementia research we don’t seem closer to finding a cure. However, in recent years, an unexpected line of evidence has emerged in how we might protect brain health. Scientists have uncovered evidence that as well as preventing shingles, vaccination against the chicken-pox virus could also prevent dementia.
What is the shingles vaccine?
The virus that causes shingles, Varicella zoster virus (VZV), is the same virus responsible for chicken-pox. After infection in childhood, VZV remains dormant in nerve cells. Later in life, the virus can reactivate, leading to shingles which results in a painful rash that can leave lasting nerve damage. For this reason, it is recommended that older people get the shingles vaccine once they turn 65.
There are two main types of shingles vaccine: Zostavax, which was widely used until the late 2010s, and Shingrix, which is currently the preferred vaccine because of stronger immunity and safety. A key difference between these vaccines is that Shingrix contains an ‘adjuvant’, an ingredient designed to enhance the vaccine’s effect.
What the studies show.
The introduction of the shingles vaccine, and then the transition to a new vaccine, have provided researchers with interesting natural experiments, in which they have been able to compare outcomes between different groups of people.
A study published in 2025, led by researchers at Stanford Medicine, looked at the Zostavax vaccine uptake in Wales. Because the vaccine was offered only to people under a certain age at a specific date, individuals born just weeks apart and were otherwise similar were split into two groups - those that got the vaccine and those who didn’t. Over seven years, the study tracked the number of dementia cases in more than 280,000 older adults. Those vaccinated had a 20% lower risk of being diagnosed with dementia than those unvaccinated. The protection appeared to be more powerful in women, who saw a 25–33% lower relative risk of developing dementia if vaccinated.
In addition to the Zostavax data, a study from University of Oxford analysed over 200,000 individuals’ health records. They compared dementia risk following the Shingrix vaccine versus the older Zostavax vaccine, and against other vaccines. They reported a 17% reduction in dementia diagnoses over six years in those given Shingrix compared with Zostavax.
There have been similar findings from over 460,000 people in Canada, over 100,000 people in Australia, and over 100,000 people in the USA. All studies showed a similar result; 17-20% reduction in dementia diagnoses for those who are vaccinated, with 3 of the 4 studies showing a more powerful effect in women. Although observational studies are considered to be a relatively weak form of research evidence, the replicability of these results in large cohorts in 4 different countries adds weight to the theory that it is indeed the vaccine that is linked to the reduction in dementia.
Emerging data hints that, as well as delaying dementia onset, shingles vaccination may also slow progression in those with established dementia. A follow-up analysis of the Welsh cohort found that among people already diagnosed, those vaccinated had lower rates of death attributed to dementia over several years.
What we don’t know.
Although the evidence is strong for an association and suggestive of causality, it is still hard to say for certain that the vaccine is the factor that influenced dementia risk without further research. For instance, those who accepted the vaccine may differ in health status, lifestyle, or care access that might influence their risk of dementia. A more controlled type of study, such as a large scale randomised controlled trial, should be able to determine the relationship more definitively. We also don’t know why women consistently seem to have a greater response to the vaccine than men, with one study (Wales) showing no benefit for men at all. Likewise, we don’t know if there is benefit in getting the vaccine at younger ages or whether getting the vaccination still shows benefits in those who have already had shingles.
If the vaccine is found to be the factor that protects against dementia, it’s not clear how it does this. However, there are a few plausible theories. Because herpes viruses like VZV can affect the nervous system by causing inflammation or other processes linked with neurodegeneration, scientists have hypothesised that suppressing VZV reactivation might reduce dementia risk. By keeping the virus dormant, the vaccine may prevent nerve inflammation or subclinical damage that over long periods could contribute to neurodegeneration.
Or, it might have nothing to do with the VZV virus at all. It could be the adjuvant that is used in the vaccine causes “off-target” effects on the immune system, reducing chronic systemic inflammation, or improving clearance of pathological proteins implicated in dementia. The stronger association seen with Shingrix, which uses a more potent immune-stimulating adjuvant than Zostvax, supports this possibility. For example, some studies have suggested that similar protective effects are seen with vaccinations for other viruses, such as RSV, that use the same adjuvants as Shingrix.
What this means for you.
Although the studies aren’t yet conclusive, they provide a compelling additional reason to get your shingles vaccine if you are eligible. As well as preventing a painful shingles episode, you may be reducing your future dementia risk.
Shingrix is a highly immunogenic vaccine, which is why it is so effective, but side effects such as a sore arm, fatigue or flu-like symptoms are common afterwards. These usually resolve within a few days and serious events are very rare.
The NHS offers the shingles vaccine to people aged 65-79 in two doses given between 6 and 12 months apart. You can get shingles more than once, so you should get the vaccine even if you've had shingles before. If you are eligible for the vaccine but haven’t been offered it, speak to your NHS GP to organise it.
Even if future clinical trials confirm a protective effect against dementia, shingles vaccination should be viewed as one part of a broader approach to healthy brain ageing, alongside well-established measures such as good blood pressure control, cardiovascular risk reduction, regular physical activity, a healthy diet, maintaining hearing, staying mentally active, and remaining socially engaged [read more here].
