Ask open-ended questions recursively. People often have a story or experience at the root of their beliefs. Uncovering that root (with your questions) also gives the anti-vaxxer an oppprtunity to ask new questions about why they believe what they believe. Generally, we need new questions to arrive at new answers.

What is Street Epistemology?

• https://www.youtube.com/watch?v=moApG7z2pkY&feature=youtu.be&fref=gc