I don’t think the term media literacy was used but we did learn literary criticism and how to formulate arguments in formal debate. We covered The Onion and adbusters, and we talked about identifying bias. In history class we learned the difference between primary and secondary sources and my history teacher was the first person I ever heard say "follow the money " to understand a person’s motivations. We also had a theory of knowledge class which taught some basics of philosophy.
I don’t have any evidence for this but it seems like the vaccine pushback is at least partially a desire to avoid responsibility. If they choose to vaccinate and their kid is in the 0.000001% who experience adverse effects then it would be their fault the kid was hurt but if they don’t vaccinate and their kid just happens to die of measles or whatever then it was all part of god’s plan and they didn’t do anything wrong.