[MagnumOpus]

Before facebook, anti-vaccine sentiment mostly spread through newspapers and TV. There were big scares, but they were only ignited after at least some "experts" found the anti-vaccine argument credibe, and public sentiment could be restored by the same experts declaring it safe. So the threshold for irrational/gossip-driven antivax sentiment was far higher, and mitigation was far easier.

See, for instance, the UK pertussis vaccine scare and whooping cough epidemic in the 1970s... [1]

[1]https://en.wikipedia.org/wiki/Vaccine_hesitancy#UK,_pertussi...