Being immunised against shingles has previously been linked to a reduced risk of dementia, and a recent study now suggests that the newer vaccine may ward off the condition even more effectively than an older version, say British researchers.
The latest vaccine, Shingrix, which has been available since 2017, reduces the risk of developing the condition in the next six years by 17% more than an older vaccine called Zostavax, reports New Scientist.
Shingles occurs when the varicella-zoster virus, which causes chickenpox and stays in the body, becomes reactivated at a time when the immune system is weakened, such as when someone is stressed or having chemotherapy. This results in a painful rash, which can sometimes get infected or scar.
With the risk of shingles increasing with age, physicians generally recommend that older people – aged 50 in the US and 65 in the UK – receive a vaccination against the virus and a booster about six months later.
Until seven years ago, the most common vaccine, Zostavax, was based on a live virus. Studies found that this appeared to be associated with a reduced risk of dementia, although connections between different types of vaccines and dementia have been the subject of controversy.
Multiple countries have started phasing out Zostavax in favour of the more effective Shingrix. This is a recombinant vaccine, where a small piece of DNA is taken from the pathogen and inserted into bacterial or yeast cells, which then produce its proteins.
These then trigger an immune response in the body.
Wanting to know how this vaccine might affect dementia risks, Maxime Taquet at the University of Oxford and his colleagues collected the medical records of 103 837 individuals in the US who were immunised after the launch of the recombinant vaccine in November 2017 and another 103 837 who were immunised prior to that.
They then selected 100 532 people in each group, average age 71, who received a shingles vaccine during each time period and excluded anyone who received both types.
When looking at the medical records after the first shingles vaccination, the team found that those immunised after November 2017 were 17% less likely to develop dementia over the next six years than those who were vaccinated before. The reduced risk may have extended beyond the six years, but a fall in the number of participants meant the researchers didn’t study that.
Women seem to particularly benefit from the newer vaccine, despite both sexes going on to have a similar rate of shingles, they wrote in their paper, published in Nature Medicine.
The reasons for the risk reduction are unclear, although it is possible that herpes zoster infections contribute to dementia, so the vaccine that more effectively protects against the virus also better wards off dementia, said Taquet.
The study is thorough and well carried out, even though it is based on medical records that do not provide other important information, such as people’s physical activities and diets, said Pascal Geldsetzer from Stanford University, California.
People who lead healthy lifestyles, which may reduce the risk of dementia, could have also waited for the more effective vaccine to come out, he added.
But Richard Lathe at the University of Edinburgh pointed out that multiple kinds of vaccines are associated with reduced dementia rates. For example, the Bacillus Calmette-Guérin (BCG) vaccine, which protects against tuberculosis and can be used to treat bladder cancer, has been linked to a 45% reduced dementia risk.
The results could therefore be due to vaccines giving the body a general immune boost rather than protection from shingles specifically reducing our dementia risk, Lathe said.
Study details
The recombinant shingles vaccine is associated with lower risk of dementia
Maxime Taquet, Quentin Dercon, John Todd & Paul Harrison.
Published in Nature Medicine on 25 July 2024
Abstract
There is emerging evidence that the live herpes zoster (shingles) vaccine might protect against dementia. However, the existing data are limited, and only refer to the live vaccine now discontinued in the USA and many other countries in favour of a recombinant vaccine. Whether the recombinant shingles vaccine protects against dementia remains unknown. Here we used a natural experiment opportunity created by the rapid transition from the use of live to the use of recombinant vaccines to compare the risk of dementia between vaccines. We show that the recombinant vaccine is associated with a significantly lower risk of dementia in the six years’ post-vaccination. Specifically, receiving the recombinant vaccine is associated with a 17% increase in diagnosis-free time, translating into 164 additional days lived without a diagnosis of dementia in those subsequently affected. The recombinant shingles vaccine was also associated with lower risks of dementia compared to two other vaccines commonly used in older people: influenza and tetanus/diphtheria/pertussis vaccines. The effect was robust across multiple secondary analyses, and present in both men and women but greater in women. These findings should stimulate studies investigating the mechanisms underpinning the protection and could facilitate the design of a large-scale randomised control trial to confirm the possible additional benefit of the recombinant shingles vaccine.
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