Can the Shingles Vaccine Prevent Dementia?

A new paper provides good evidence that the shingles vaccine can prevent dementia, which strongly suggests that some forms of dementia are caused by the varicella zoster virus (VZV), the virus that on initial infection causes chickenpox. The data come from Wales where the herpes zoster vaccine (Zostavax) first became available on September 1 2013 and was rolled out by age. At that time, however, it was decided that the vaccine would only be available to people born on or after September 2 1933. In other words, the vaccine was not made available to 80 year olds but it was made available to 79 year and 364-day olds. (I gather the reasoning was that the benefits of the vaccine decline with age and an arbitrary cut point was chosen.)

The cutoff date for vaccine eligibility means that people born within a week of one another have very different vaccine uptakes. Indeed, the authors show that only 0.01% of patients who were just one week too old to be eligible were vaccinated compared to 47.2% among those who were just one week younger. The two groups of otherwise similar individuals who were born around September 2 1933 are then tracked for up to seven years, 2013-2020. The individuals who were just “young” enough to be vaccinated are less likely to get shingles compared to the individuals who were slightly too old to be vaccinated (as one would expect if the vaccine is doing it’s job). But, the authors also show that the individuals who were just young enough to be vaccinated are less likely to get dementia compared to the individuals who were slightly too old to be vaccinated, especially among women. A number of robustness tests finds no other sharp discontinuities in treatments or outcomes around the Sept 2, 1933 cut point.

The following graph summarizes. The top left panel shows that the cutoff led to big differences in vaccine uptake, the top right panel shows that there was a smaller but sharp decline in dementia in the vaccinated group. The bottom panel shows that was no discontinuity in a variety of other factors.

Read the whole thing.

I have had my shingles vaccine. As I have said before, vaccination is the gift of a superpower.


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