I like your comment, and it’s kind of comforting - because it means we don’t have to worry too much, as you suggest the anti-vaxxers are like a neat little self-contained cult who don’t venture out of their compound.

However, in reality, it’s probably a gradual process of belief change or formation - people don’t move from slightly unsure to frothing-at-the-mouth anti-vaxxer overnight. And this sort of disinformation may well be accessed and become influential to people who are part-way through that process.