Shingles shot could be a simple way to delay dementia

Vaccination with GSK's recombinant shingles vaccine, Shingrix, could delay the onset of dementia, according to researchers in the UK.

A study published in Nature Medicine suggests that people administered Shingrix have a lower risk of dementia compared to those given Zostavax - an older shingles shot based on a different technology – and builds on earlier research suggesting a benefit from this type of vaccination.

The observational study used information from health records involving more than 200,000 people living in the US who had received either the 'live' jab Zostavax (now discontinued in the US) or recombinant Shingrix and compared the risk of dementia in each group over a six-year year period.

They found that people receiving Shingrix vaccine had a 17% reduction in the onset of dementia – equivalent to a delay of 164 days before a diagnosis – compared to those given Zostavax.

The benefit was seen in both men and women but was slightly higher in the latter, and while the delay is just a few months could have tangible benefits from a public health perspective, according to the scientists.

Shingrix was also associated with lower risks of dementia compared to two other vaccines commonly used in older people, influenza and tetanus/diphtheria/pertussis vaccines, according to researchers from the University of Oxford and University College London.

While observational studies of this type can only ever give an indication of a benefit that needs to be followed up in prospective studies, the findings are consistent with the earlier Zostavax studies and have led to calls for a large-scale randomised controlled trial to test the hypothesis.

It remains ujust how the vaccines may be reducing risk, but one possibility is that the herpes zoster virus that the vaccines target may be a factor. These are often contracted in childhood as a case of chickenpox but can reactivate in later life to cause shingles, a painful and potentially serious condition that causes a blistering rash.

It's possible that reactivation could in some way promote dementia, although there are other possibilities, including for example that the immune response induced by the vaccines has an impact on the pathology of some forms of dementia like Alzheimer's disease.

"The findings are intriguing and encouraging," said Prof Paul Harrison of Oxford University, who led the study. "Anything that might reduce the risk of dementia is to be welcomed, given the large and increasing number of people affected by it."

In the US, people aged 65 and over are routinely immunised against shingles, while in the UK, a free shingles vaccine is available to people who turn 65, those aged between 70 and 79, and anyone over 50 who has a severely weakened immune system.

Prof Andrew Doig of the University of Manchester, who was not involved in the study, said the results are "convincing" and suggest shingles vaccination is "comparable in effectiveness to the recent antibody drugs for Alzheimer's disease."

Evidence is now building for a placebo-controlled clinical trial of Shingrix, and suggested it may be beneficial to give the vaccine earlier, given that the path to dementia can start decades before symptoms emerge, he added.

"A link between infection with the herpes zoster virus and the onset of dementia has been suspected for some time. As well as vaccines, a trial of the antiviral drug valacyclovir against Alzheimer's disease is currently underway," noted Prof Doig.