Distrust of government and authorities is a big factor. You have much more vaccine hesitancy in the U.S. than in Nordics (high-trust societies); Russians and Bulgarians are extremely sceptic of their governments, and extremely sceptic of vaccines.
https://ourworldindata.org/explorers/coronavirus-data-explor...
I have seen Trump boast about vaccines, in his usual distasteful way. I have seen him recommend vaccines. I have not seen him disparage or discourage vaccinations (though he's been extremely clumsy, as he was with everything).
It seemed to me that originally, when Trump boasted about the vaccines, his political opponents (the Democrats in US, and others elsewhere) were the ones who were sceptical about vaccine development - simply because of this tribalism.
(Note: I'm not American, not in either tribe.)
And in what timescale, 2 generations?
I think a big part of the issue are some members of the older generations who left school long ago when there was maybe one newspaper in town. The internet, which came much later, gives everyone a voice and allows every idiot to dress stuff up, make it look professional, put lipstick on it and amplify it with the click of a button. How do you know to apply critical doubt to someone's claims when you don't even know how damn easy it is to produce a convincing fake? And if you do have a doubt, how would you even start fact-checking when all you know is Facebook and Youtube?
Too many people have their guard down, sitting in the comfort of their living room browsing The Algorithm, and don't even realize they are being attacked.
In almost all conspiracy theories, one side has a lot of facts, the other has a lot of “feelings”. If you try having a conversation with someone who believes in some conspiracy you’ll eventually get to “I just don’t feel…”