The anti-vax is one part truth (vaccination programs are used as cover for depopulation) and one part fiction (vaccines themselves are unscientific and the concept of vaccination is eugenic in purpose). The former is the hook, but large quantities of anti-vax literature emphasize the latter and obsessively focus on an alternate science, rather than the truth. The usual pattern is that Bill Gates said something about reducing population through vaccine programs - which is something he did say, loudly and proudly - and thus the problem is you must reject vaccines altogether, and that the vaccines are "bad genes". In doing so, they have turned resistance against abuses committed by the organizations, into an idealist argument that leads nowhere. This then is used to sell an "alterna-eugenics" which fills the incredulous, outraged dissident with the same principles as a eugenist, and wastes their effort looking at the vaccine and the biological rather than acknowledging what is really happening.
It doesn't always go like this, and qualified scientists have cast doubt on whether vaccination itself works, or exposed how Bill Gates is further depopulation goals in Africa. (The latter is more or less an openly admitted, common knowledge goal, going back to the 1960s and the new way imperialism was going to work. LBJ would say outright that poor countries better get with population control programs or else, and that it was an open agenda for US foreign policy.) But if the eugenists can put shit like NaturalNews at the top of the search index, and can create an echo chamber where outraged citizens read of atrocities and are supplied with a false answer, it becomes self-perpetuating.
The silly thing about rightoids is that they're so confused that they don't even get their own leaders hold them in open contempt. Almost all of these churches that speak of anti-vax are taking money and look the other way when it happens to some poor heathen brown person. The alterna-eugenics helps the rightoid accept that such programs are actually good if they're used against the "bad people" (i.e., poor brown people), and also gets the rightoid to accept the inevitability of poor people being sterilized.
That said, more of the rightoids aren't even opposed to sterilization, because now overt Hitlerism has been legitimized. They just laugh and say the poor people deserve it, then they avoid the vaccinations because they feel they don't need it.