Shingles vaccination appears to reduce risk of dementia

A very interesting paper published last week in Nature reports a 20% reduction in the risk of getting dementia for up to seven years after getting vaccinated against shingles (herpes-zoster) with a live virus vaccine (Zostavax). As described in a more lay-reader-friendly article by Pam Belluck in the New York Times, this study emerged from an unusual aspect of a shingles vaccine rollout in Wales on Sept. 1, 2013. Initially, there was not enough vaccine available to  immunize everyone who wanted it, so those born before 2 September 1933 were arbitrarily deemed ineligible and remained ineligible for life, whereas those born on or after 2 September 1933 were deemed eligible for at least one year to receive the vaccine. To limit the likelihood of differences between the groups, researchers used statistical analysis to more heavily weigh data from people just one week on either side of the cutoff: those who turned 80 in the week before rollout and those who turned 80 in the week after. The age cutoff — imposed because of a limited supply and because the vaccine was then considered less effective for people over 80 — set up a “natural experiment” to provide causal rather than simply correlational evidence that getting the shingles vaccination lowers risk of getting dementia by 20%, at least for seven years. Although the mechanism by which shingles infection promotes dementia is not certain, it most likely involves inflammatory damage to the brain.

The live virus shingles vaccine (Zostavax) was replaced in 2017, at least in the US, by a recombinant shingles vaccine called Shingrix. Shingrix has a vaccine efficacy of 97.2% compared to placebo, while Zostavax reduced the risk of developing shingles by 51%. Early signs suggest that Shingrix is even more effective than Zostavax in slowing progression of dementia. 

On a personal note, I had been reluctant to get vaccinated against shingles largely because of the common reports of unpleasant side effects, but last year I bit the bullet and got the series of two Shingrix shots. It really wasn’t bad, just some muscle aches and sore injection site, but everything was better in 24 hours. If you are over 50 and especially if you have any risk factors for dementia, I urge you to get vaccinated.