I remember about ten years ago, back when I still had a Facebook account, I stumble onto a Facebook group titled something like "Moms concerned about Child Health" (or something similar). I was curious what that actually meant, and looked into it, and it was basically a big anti-vax group, and they didn't like the polio vaccine.
The sentiment there seemed to be "your kid isn't going to get polio, don't vaccinate them, vaccines cause autism". I don't know really how popular the sentiment was before the conservative idiots co-opted anti-vax rhetoric after COVID, but they definitely existed.
ETA:
Not saying being conservative makes you an idiot, but I do think that it was primarily conservative idiots that spread anti-vax propaganda during and after COVID.
I don't know about popular, but they were certainly around. Probably a factor in the ending of use of thimerosal, an ethylmercury based preservative, in vaccines. It was easier to remove that, then to convince some of the anti-vax people that ethylmercury is rapidly eliminated from the body and does not go back in time to give someone autism before they got a vaccine.
That said, the medical community and the internet are not always kind and empathetic. Some kids are really miserable when they get a vaccine and when they do their job and induce an immune reaction, that can be miserable too. If your kid has big reactions, spacing out and prioritizing the vaccines a bit can be helpful. Delayed compliance is better than non-compliance. And there's a lot of people who refuse to accept that there's any risk; it's managable and reasonable, but it's still there and pretending there's no risk plays into the narrative when someone does have a complication.
I dispute that last point. Literally every vaccine I've ever seen has exemptions for medical reasons. That's why medical professionals always strive for herd immunity.
I'm sure there are a few idiots that claim that there's never been a side effect for anyone from a vaccine, but I've never met them.
Disinformation campaigns can be powerful and effective. See the sites below for examples of this disinformation. There are fools that believe this stuff.
They will oppose it until they get cancer and then it will be too late and they will cry about government conspiracy keeping them from accessing life saving vaccines.
