You are mixing things together that don't belong together. Covid is very new and scientific discussion is still ongoing. There is no consensus. Anti-vaxxers are about tried and proven vaccines they don't trust.
I think as with other things (like religion), people get mostly "infected" by their peer group. Also there are certain aspects that make memes prevail, like fear and protectiveness of one's own children in the case of vaccines. It's not simply a matter of exposure to YouTube videos.