Canada

There are plenty of them still around—much of the Boomer generation was in elementary school before widespread administration of MMR and polio vaccines, or at least knew people a few years older who were. Thing is, they're not the ones making the decisions about whether to vaccinate youngsters these days. Their own kids—GenX like me (and I suspect you as well), and some early Millenials—all got the vaccines.

People have been growing up with a government that lies ever more to them. People have grown up with a government that has purposefully done things that end up being harmful, lied about it, and then the truth comes out - only those same people have been austrasized by being labelled conspiracy nuts - and no one stopped to apologize.

And then the entire situation with Covid and the Covid Vaccine, where yes - depending on health conditions, that damn thing had a serious risk to some people's health and we were lied to. Some of the issues are related to accidental poor injection which we have had techniques that would have wasted like a tiny % of vaccine doses but avoid all kinds of complications. Then we had people stuck on ventilators for far too long which leads to long term health complication concerns but we were all being told no it's fine - but then the information comes out.

Flat Earthers, Anti-Vaccers, and so on don't come out of no where - it comes from a place of strong distrust in authorities that are pushing such information. And especially the Trudeau Government over the last decade has smashed trust in the federal government. And some actions taken by provincial governments have strained trust - with very few Politicians Publicly apologizing for missteps taken during the Pandemic.

TL;DR: Our current Federal Government smashed trust with a lot of people, and that is going to bring into question anything and everything they push - no matter how good or bad. And with the Lack of family doctors in many area's, few people have trusted sources of good information to turn to, leading to a rise in Anti-vaccination, and other movements.