SHINGLES vaccination reduced the probability of new dementia diagnoses by around one-fifth over seven years, according to a large-scale study from Wales.
Researchers were able to take advantage of a shingles vaccine policy where people born on or after 02 Sep 1933 were eligible for shingles vaccination from 01 Sep 2013, whereas those born before this date were not eligible.
This allowed researchers to compare two groups of people who differed in age by just a few weeks but could otherwise be expected to be fairly similar.
When they compared new dementia diagnoses between the vaccine-eligible and ineligible populations, they found that receiving the vaccine decreased the likelihood of being diagnosed with dementia during the seven-year follow-up by approximately 20%.
The effect was greater in women than in men.
The authors proposed potential mechanisms to explain how zoster vaccination might reduce the risk of dementia, such as reduced reactivation of dormant zoster virus or a broader immune mechanism triggered by the vaccine.
Further research is needed to determine whether the effects are truly causal and to understand how protection is conferred.
"Although it is still unclear precisely how herpes zoster vaccination lowers the risk of dementia, the implications of the study are profound," said Anupam Jena, Professor of Health Care Policy at Harvard Medical School, in an accompanying editorial.
"The vaccine could represent a cost-effective intervention that has public health benefits strongly exceeding its intended purpose."
Dr Henry Brodaty, Professor of Ageing and Mental Health at the University of New South Wales, highlighted the fact that the vaccine used was the live-attenuated vaccine (Zostavax), and it's unclear whether the newer non-live virus Shingrix, which is used widely in Australia, will have the same effect.
He also noted that the recipients were around 80 when vaccinated, and further research will need to determine whether immunisation at younger ages, as per the National Immunisation Program protocol in Australia, will be just as effective.
"There has been evidence for some time that older people who receive their vaccinations in general are less likely to develop dementia," said Professor Brodaty.
"This is the best evidence yet to show this."
Read the full paper HERE. KB
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