Researchers have raised hopes of slowing dementia after finding that a recently approved shingles vaccine was linked to a significant reduction in diagnoses of the condition in the six years after receiving the shot.
The discovery, based on US medical records, suggests that apart from the health benefits of preventing shingles, a painful and sometimes serious condition in the elderly, 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 of the study, said the results support the idea that shingles vaccination can 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 chicken pox. When a shingles vaccine, Zostavax, was first introduced in 2006, a number of studies found hints that the risk of dementia was lower in those who received the injections.
The development of a new and more effective shingles vaccine, Shingrix, led to a rapid switch in the US in October 2017, meaning that those 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 against 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 to Zostavax.
For those who have developed dementia, this amounts to an extra 164 days, or almost six months, without the condition. The effect was stronger in women, at 22%, than in men with 13%.
The researchers went on to examine dementia rates in people who received other vaccines. Write in Naturopathy, they describe how those given Shingrix had a 23 to 27% lower risk of dementia than people vaccinated against influenza, tetanus, diphtheria or whooping cough. One of the authors of the study, Prof John Todd at Oxford, is a consultant to GSK, the maker of Shingrix, but the researchers said the study was carried out without any involvement from the pharmaceutical company, which was informed of the work when accept it for publication.
Last year, the NHS made Shingrix available to people turning 65. “The expectation is that if it is indeed a causal effect, we will see a reduction in dementia in the UK once people start using the Shingrix vaccine,” said Taquet.
There are more than 55 million people worldwide living with dementia and more than 900,000 in the UK alone. One in three people will develop the condition in their lifetime, and although drugs that appear to slow the disease have recently been approved, there is no cure.
The latest study does not prove that Shingrix slows dementia, but Prof Paul Harrison, a senior author on the paper, said more groups were working on the question. If the vaccine protects 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 stronger, play a role.
It is also unclear 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 this data is published, which more people choose to take [Shingrix] when they are offered it,” Harrison said. “I certainly wouldn’t recommend that people start demanding the vaccine just because they think it will reduce the risk of dementia.”
Andrew Doig, a professor of biochemistry at the University of Manchester, said: “This is a significant result which is comparable in effectiveness to the recent antibody drugs for Alzheimer’s disease. The administration of the recombinant shingles vaccine could be a simple and be an inexpensive way to lower the risk of Alzheimer’s disease.
“Now we need a clinical trial of the [new] vaccine, comparing patients receiving the vaccine with those receiving a placebo. This is the most reliable way to find out how well the vaccine is working. We also need to see how many years the effect can last and whether we should vaccinate people at a younger age. We know that the road to Alzheimer’s disease can begin decades before any symptoms are apparent, so the vaccine may be even more effective if given to people in their 40s or 50s.”
