I don't think you can reasonably conclude either that a) anti-vaxxer propaganda is effective insofar it attracts statistically significant number of new people under its bannder, or b) that FB blocking their pages effectively reverses the effect of (a).
Personally, I hold the opinion that anti-vaxxers are more of a natural product of their environments than anything else. You can clearly see the distinction along the religious and educational boundaries, for example. Limiting the freedom of speech in attempt to silence them is not going to work, like it's not working in stopping any other kind of speech you don't like. Censorship is dangerous: it alienates people and prevents communication, effectively radicalizing those affected.
Deplatforming has proved very effective, at least in the cases of ISIS[1], and I would argue deplatforming Trump has helped to deescalate tensions to some degree (or at least, given the media something else to talk about than his rants).
Whether it’s the right choice is obviously subject to debate.
Personally, I hold the opinion that anti-vaxxers are more of a natural product of their environments than anything else. You can clearly see the distinction along the religious and educational boundaries, for example. Limiting the freedom of speech in attempt to silence them is not going to work, like it's not working in stopping any other kind of speech you don't like. Censorship is dangerous: it alienates people and prevents communication, effectively radicalizing those affected.