As far as i know the fear of vaccines started growing because of Andrew Wakefield.
Andrew Wakefield developed a vaccine against measles, however the MMR vaccine was already on the market doing its job just fine. So how could he make sure that his vaccine was taken instead of the MMR?
He had to start lying. So he started to spread the notion that the MMR vaccine would cause autism. My memory hets fuzzy from here on but basically it was MMR vaccine causing autism because it would mess with gut bacteria and to prove that he was messing with data and his colleagues and until they realized what was happening the damage was already done. And over time the lie from Wakefield turned into the commonly known “vaccines cause autism”.