FWIW I think Trump #1 (45) wasn't an anti-vax presidency; it might have been suspicious of healthcare professionals (for the good reason that so many people know opioid epidemic victims) and he was always a bit equivocal around hydroxychloroquine and bleach and "powerful light inside the body" but Trump didn't start to lean antivax until not long after Biden took over.

(And let's be clear: Operation Warp Speed was an enormous success even if Trump is an ignoramus)

Some of that might have been expediency — Biden was catching shit from the antivax and healthcare-skeptical movement and moving in on that would be easy — but Trump has always been vulnerable to being influenced by people and RFK Jr appears to be generally so much more persuasive than bears thinking about, so he was a factor later on.

Trump #2 (47) is fully an anti-vax presidency; even Hegseth backed away from flu vaccine mandates, only to have an outbreak in an Army (IIRC?) facility.