Study raises hope that shingles vaccine could delay the onset of dementia
Researchers have raised hopes that dementia can be delayed after finding that a recently approved shingles vaccine was linked to a significant reduction in diagnoses of the condition in the six years following the shot.
The finding, based on US medical records, suggests the vaccine not only offers health benefits by preventing shingles, a painful and sometimes serious condition in older people, but could also delay the onset of dementia, the leading cause of death in the UK.
Dr Maxime Taquet from the University of Oxford, the study’s lead author, said the results supported the idea that shingles vaccination could prevent dementia. “If these findings are validated in clinical trials, they could have important implications for older people, 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 the shingles vaccine, Zostavax, was first rolled out in 2006, a number of studies found evidence that the risk of dementia appeared to be lower in those who received the vaccinations.
The development of a new and more effective shingles vaccine, Shingrix, led to a rapid switch in the U.S. in October 2017. People vaccinated before that date were given Zostavax, while people vaccinated afterward were more likely to receive Shingrix.
The Oxford team studied the medical records of more than 200,000 U.S. citizens who had been vaccinated against shingles, about half of whom had received the new vaccine. Over the next six years, the risk of dementia was 17 percent lower in those who received Shingrix compared with Zostavax.
For those who developed dementia, that equates to 164 extra days, or almost six months, 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 Naturopathythey describe how those who received Shingrix had a 23 to 27 percent lower risk of dementia than people who had been vaccinated against flu, tetanus, diphtheria or whooping cough. One of the study authors, Prof John Todd of Oxford, is a consultant to GSK, the manufacturer of Shingrix, but the researchers said the study was conducted without any involvement from the pharmaceutical company, which was 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, we would see a reduction in dementia in the UK once people started taking the Shingrix vaccine,” Taquet said.
More than 55 million people worldwide are living with dementia, with more than 900,000 in the UK alone. One in three people will develop the condition in their lifetime and although drugs have recently been approved that appear to slow the disease, 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 that 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 the virus in shingles causes pathological changes that lead to dementia. Another possibility is that chemicals called adjuvants in the vaccine, which boost the immune response to the vaccine, play a role.
It is also unclear whether protection against dementia would be more effective if the vaccine were given to younger people, such as those in their fifties, or whether the effect would disappear too quickly.
“It will be interesting to see if this data is made public that more people choose to take (Shingrix) if they are offered it,” Harrison said. “I certainly would not recommend that people demand the vaccine just because they think it will reduce the risk of dementia.”
Andrew Doig, professor of biochemistry at the University of Manchester, said: “This is a significant result, comparable in effectiveness to recent antibody drugs for Alzheimer’s disease. Administering the recombinant shingles vaccine could be a simple and cheap way to reduce the risk of Alzheimer’s disease.
“Now we need to do a clinical trial of the (new) vaccine, comparing patients who get the vaccine with patients 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 lasts and whether we need to vaccinate people at a younger age. We know that the path to Alzheimer’s can start decades before symptoms are visible, so the vaccine could be even more effective if given to people in their 40s or 50s.”