The shingles vaccine given to people on the NHS could delay the onset of dementia, according to a new study.

The finding – which experts say is “convincing” – shows the Shingrix vaccine is linked to at least a 17% drop in dementia diagnoses in the six years after vaccination than the previously-used Zostavax jab.

University of Oxford researchers said people could expect five to nine more months of life without dementia for those given the Shingrix jab compared with other vaccines.

Both men and women benefited from the newer jab, but the effects were greater in women, the study found.

Shingles is a common condition that causes a painful rash.

It can sometimes lead to serious problems such as deafness, long-lasting pain, and blindness.

Shingles occurs most often as people get older and is more likely to cause serious problems in older age groups.

Dr Maxime Taquet, academic clinical lecturer in the department of psychiatry at Oxford, who led the study on more than 200,000 people, said: “The size and nature of this study makes these findings convincing and should motivate further research.

“They support the hypothesis that vaccination against shingles might prevent dementia.

“If validated in clinical trials, these findings could have significant implications for older adults, health services and public health.”

John Todd, professor of precision medicine at the University of Oxford’s Nuffield Department of Medicine, said: “A key question is, how does the vaccine produce its apparent benefit in protecting against dementia?

“One possibility is that infection with the Herpes zoster virus (shingles) might increase the risk of dementia and, therefore, by inhibiting the virus the vaccine could reduce this risk.

“Alternatively, the vaccine also contains chemicals which might have separate beneficial effects on brain health.”

Dr Taquet said the team’s interpretation of the data is that the jab works to delay dementia rather than prevent it altogether, although more work is needed.

On the NHS, people are offered two doses of Shingrix when they turn 65, as long as their birthday was on or after September 1 2023.

Those who turned 65 before this date are eligible for the shingles vaccine when they become 70, while all people aged 70 to 79 are also eligible.

People aged 50 and over with a severely weakened immune system are offered a vaccine.

Evidence shows Shingrix, made by GlaxoSmithKline (GSK), can provide at least a decade of protection against shingles after the first jab.

For the new study, published in the journal Nature Medicine, researchers wanted to use emerging but limited evidence that the previous vaccine, Zostavax, might also protect against dementia.

In the US, Zostavax was replaced by Shingrix in October 2017, giving a good opportunity to compare the two vaccines.

Researchers looked at people’s risk of dementia in the six years following the introduction of Shingrix and compared them with otherwise similar people who had received Zostavax.

Some 103,837 people were in each group.

Shingrix was also compared with people who had received vaccines against other infections (flu and tetanus, diphtheria and pertussis).

While research into whether vaccines affect dementia risk continues, people should be aware that there are other factors that have definitively been linked to an increased dementia risk. These include things like smoking, high blood pressure and excessive alcohol consumption

The results showed Shingrix was associated with a 17% lower risk of dementia than Zostavax, and 23%-27% less than with the other vaccines.

There was more benefit in women than men, with women enjoying 22% versus 13% more time lived without a diagnosis of dementia.

Dr Sheona Scales, director of research at Alzheimer’s Research UK, welcomed the study but said further research was needed.

She said it “isn’t clear how the vaccine might be reducing risk, nor whether the vaccine causes a reduction in dementia risk directly, or whether there’s another factor at play”.

She added: “While research into whether vaccines affect dementia risk continues, people should be aware that there are other factors that have definitively been linked to an increased dementia risk.

“These include things like smoking, high blood pressure and excessive alcohol consumption.”

The UK Health Security Agency (UKHSA) no longer supplies Zostavax but there may still be a small number of doses in GP surgeries for use.