The vaccine against Herpes zoster may also have another beneficial effect: in addition to protecting against the disease, the so-called shingles, it appears to reduce the risk of developing some form of dementia. According to a new study from the University of Oxford published in the journal Nature Medicine, in the six years following vaccination (recommended for the elderly, over 65) dementia diagnoses would be reduced by about 17%.
In the past, several studies had already identified a possible link between the Herpes zoster vaccination carried out with a previous, now obsolete vaccine, and a lower incidence of Alzheimer’s and other forms of dementia. In that case, the studies carried out never allowed definitive conclusions to be drawn, due to rather ambivalent results. With the arrival of a new recombinant vaccine, Shingrix, approved in recent years, Oxford researchers seized the opportunity to verify whether the new preparation, in addition to being more effective in preventing the onset of shingles, also showed a clearer protective effect against dementia.
Shingrix proved more effective in preventing dementia
Their study involved more than 200,000 American adults, and was conducted during the years of transition between the old and new shingles vaccines. The researchers assessed dementia diagnoses in about 100,000 participants who received the new vaccine, Shingrix, starting in October 2017 (the year the transition occurred in the United States), and compared them to those of the same number of people who had been vaccinated with the old vaccine since 2014.
In comparison, Shingrix proved more effective than the previous vaccine in preventing dementia: the risk of developing one in the six years following vaccination was 17% lower. Compared to other vaccinations for seniors, such as the flu vaccine, the incidence of dementia was 23-27% lower. The benefits emerged for both sexes, but more marked in women. According to the authors of the study, the analyses carried out make the data robust, although targeted studies will be needed to consider recommending vaccination specifically for this therapeutic indication.
While the beneficial effects of vaccines in preventing dementia seem to be proven, there is no certainty about the mechanisms from which they originate, for now. It could depend on the effects of vaccines on the immune system, as well as revealing itself as a side effect of the lower risk of viral infections, which in many cases – such as Herpes simplex, very similar to zoster – are known risk factors for the development of dementia. Again, further research will be needed to have the answer.