I think it is a reference to a study earlier this year that found that vaccine hesitancy was greatest among PhDs: https://www.usnews.com/news/health-news/articl

I think it is a reference to a study earlier this year that found that vaccine hesitancy was greatest among PhDs: https://www.usnews.com/news/health-news/articles/2021-07-27/whos-most-likely-to-refuse-a-covid-vaccine https://www.usnews.com/news/health-news/articles/2021-07-27/...