A study released on Wednesday finds that a live-virus vaccine that limits shingles symptoms was associated with a drop in the risk for dementia when it was introduced. The work took advantage of the fact that the National Health Service Wales made the vaccine available with a very specific age limit, essentially creating two populations, vaccinated and unvaccinated, separated by a single date. And these populations showed a sharp divide in how often they were diagnosed with dementia, despite having little in the way of other differences in health issues or treatments.
What a day
This study didn’t come out of nowhere. There have been a number of hints recently that members of the herpesvirus family that can infect nerve cells are associated with dementia. That group includes Varicella zoster, the virus that causes both chicken pox and—potentially many years after— shingles, an extremely painful rash. And over the past couple of years, observational studies have suggested that the vaccine against shingles may have a protective effect.
But it’s extremely difficult to do a clinical trial given that the onset of dementia may happen decades after most people first receive the shingles vaccine. That’s why the use of NHS Wales data was critical. When the first attenuated virus vaccine for shingles became available, it was offered to a subset of the Welsh population. Those who were born on or after September 2, 1933, were eligible to receive the vaccine. Anyone older than that was permanently ineligible.