You're either young or not American. Rand Paul has been anti vaccination forever
https://www.pbs.org/newshour/politics/rand-pauls-vaccine-claims-microscope
"On Friday night in Iowa, Paul faced likely voters in the state's leadoff nominating caucuses for the first time since answering questions about a measles outbreak centered in California. Paul said Monday that he had heard about "many tragic cases" of children who got vaccines and ended up with "profound mental disorders."
That assertion has no basis in medical research, and Paul clearly was still upset on Friday about how his comments had been received"
This is from early 2015, before COVID btw.