Pick any rabbit hole you want. I’m not sure it is too recent of a trend. Many want to blame the COVID situation but I remember reading an article many years ago about vaccine hesitancy and proximity to a Whole Foods Grocery. Then you get a few celebrities screaming about autism and vaccines which adds to it. The only correlation I"ve seen on that front deals with Tylenol usage during pregnancy but it was an initial low numbers paper. Then announce that the measles has been eradicated and people think they don’t need it anymore.
The only concern I have about vaccines I didn’t realize had changed since residency training/ medical school. Hey, come in for you 10 vaccines in 1 shot because both parents are working and we can’t space things out over several months like we used to. Hyperbole yes but not far off.
Not any one big thing but multiple small ones.