Shingrix is a onetime vaccination, given in two doses a few months apart. The CDC recommends it starting at age 50 for most people but also for younger adults with certain immune-weakening conditions – including those who years ago got that first-generation shingles vaccine. Fewer than 40% of eligible Americans have gotten vaccinated.

Several previous studies have suggested that shingles vaccinations might reduce dementia risk, but most could not exclude the possibility that people who get vaccinated might have other dementia-protective characteristics, like healthier lifestyles, better diets or more years of education.

According to researchers from Stanford University, health records of nearly 300,000 older adults in Wales revealed that those who received a shingles vaccine called Zostavax were 20 per cent less likely to be diagnosed with dementia over the next seven years than those who went without.