I read about it during a different election cycle. I remember it so clearly because an otherwise sensible friend suddenly started talking about how vaccines didn’t work when I mentioned it to her.

https://www.washingtonpost.com/news/post-politics/wp/2016/07/29/jill-stein-on-vaccines-people-have-real-questions/

https://www.nbcnews.com/politics/politics-news/green-party-s-jill-stein-people-don-t-trust-vaccine-n620216

https://www.uab.edu/studentmedia/?view=article&id=779&catid=23