Shingles is most common in older adults and can cause severe pain and rashes. Shingles is caused by the reawakening of inactive varicella zoster virus (VZV), the herpesvirus that causes chickenpox and which is present in most people. With that in mind, epidemiologist Pascal Geldsetzer at Stanford University in California and his colleagues turned to a natural experiment: a shingles vaccination programme in Wales, which began on 1 September 2013. Research has also suggested that those vaccinated against certain viral diseases are less likely to develop dementia 4.Īre infections seeding some cases of Alzheimer’s disease?īut all these epidemiological studies have shared a key problem: people who get any type of vaccination tend to have healthier lifestyles than those who don’t 5, meaning that other factors could account for their lowered risk of diseases such as Alzheimer’s. But recent work has suggested that people infected with viruses that affect the brain have higher rates of neurodegenerative diseases 3. The theory has been controversial among Alzheimer’s researchers. The idea that viral infection can play a part in at least some dementia cases dates back to the 1990s, when biophysicist Ruth Itzhaki at the University of Manchester, UK, and her colleagues found herpesviruses in the brains of deceased people with dementia 2. “Even a modest reduction in risk is a tremendous impact.” Dementia–infection link “If it is true, it’s huge,” says Alberto Ascherio, an epidemiologist at Harvard University in Cambridge, Massachusetts, who was not involved in the study. The study was published on the medRxiv preprint server on 25 May and has not yet been peer reviewed. But some puzzling aspects of the analysis have stirred debate about the work’s robustness. The analysis found that getting the vaccine lowers the risk of dementia by 20%. Vaccination against shingles might also prevent dementia, such as that caused by Alzheimer’s disease, according to a study of health records from around 300,000 people in Wales. The shingles vaccine Zostavax was rolled out in Wales starting in 2013.

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