Researchers have raised hopes for delaying dementia after finding that a recently approved shingles vaccine was linked to a substantial reduction in diagnoses of the condition in the six years after receiving the shot.
The discovery, based on US medical records, suggests that beyond the health benefits of preventing shingles, a painful and sometimes serious condition in elderly people, the vaccine may also delay the onset of dementia, the UK’s leading cause of death.
Dr Maxime Taquet at the University of Oxford, the first author on the study, said the results supported the idea that shingles vaccination may prevent dementia. “If validated in clinical trials, these findings could have significant implications for older adults, health services, and public health.”
Shingles is caused by the herpes zoster virus and can flare up in people who have previously had chickenpox. When a shingles vaccine, Zostavax, was first rolled out in 2006, a number of studies found hints that the risk of dementia seemed to be lower in those who got the shots.
The development of a new and more effective shingles vaccine, Shingrix, led to a rapid switch in the US in October 2017, meaning those who were vaccinated before that date received Zostavax, while those vaccinated after tended to have Shingrix.
The Oxford team studied the health records of more than 200,000 US citizens vaccinated for shingles, about half of whom received the new vaccine. Over the next six years, the risk of dementia was 17% lower in those who received Shingrix compared with Zostavax.
For those who went on to develop dementia, that amounts to an extra 164 days, or nearly six months, lived without the condition. The effect was stronger in women, at 22%, than in men at 13%.
The researchers went on to examine dementia rates in people who received other vaccines. Writing in Nature Medicine, they describe how those given Shingrix had a 23 to 27% lower risk of dementia than people who were vaccinated against flu, tetanus, diphtheria or pertussis. One of the authors of the study, Prof John Todd at Oxford, is a consultant to GSK, the manufacturer of Shingrix, but the researchers said the study was conducted without any involvement from the pharma company, who were informed of the work when it was accepted for publication.
Last year, the NHS made Shingrix available to people turning 65. “The expectation is that if this is indeed a causal effect, then we would see a reduction in dementia in the UK once people start taking up the Shingrix vaccine,” said Taquet.
There are more than 55 million people globally living with dementia and more than 900,000 in the UK alone. One in three people will develop the condition in their lifetime, and while drugs that appear to slow the disease have recently been approved, there is no cure.
The latest study does not prove that Shingrix delays dementia, but Prof Paul Harrison, a senior author on the paper, said more groups were working on the question. If the vaccine does protect against dementia, it is unclear how. One possibility is that the resurgence of virus in shingles drives pathological changes that lead to dementia. Another is that chemicals called adjuvants in the vaccine, which make the immune response to the vaccine more potent, play a role.
Also unclear is whether any protection against dementia would be more effective if the vaccine were given to younger people, such as those in their 50s, or whether it would wear off too soon.
“It will be interesting to see if these data become publicised, that more people choose to take [Shingrix] when they’re offered it,” said Harrison. “I certainly wouldn’t recommend that people should start demanding the vaccine just because they think it’ll reduce the risk of dementia.”
Andrew Doig, a professor of biochemistry at the University of Manchester, said: “This is a significant result, comparable in effectiveness to the recent antibody drugs for Alzheimer’s disease. Administering the recombinant shingles vaccine could well be a simple and cheap way to lower the risk of Alzheimer’s disease.
“Now, we need to run a clinical trial of the [new] vaccine, comparing patients who receive the vaccine with those who get a placebo. This is the most reliable way to find out how well the vaccine works. We also need to see how many years the effect might last and whether we should vaccinate people at a younger age. We know that the path to Alzheimer’s disease can start decades before any symptoms are apparent, so the vaccine might be even more effective if given to people in their 40s or 50s.”
