Trump is pretending now to be pro-vaccine, and owning it, claiming it, because he has more chance to motivate THE SHEEP to be wary of it doing that, than he does to lose reputation with anyone who works this out for themselves. Trump is offering himself up for sacrifice in a sense because he is willing to help attract criticism of the vaccine. Those who disagree with Trump's pretended position are against the vaccine will not take it and not be at risk from it for now. But those who might question the vaccine could be put-off if it meant "agreeing with Trump" so Trump cannot be antivax openly.
There is even the chance some will stay away just because he pretends to like it. Kamala even said - "If the vaccine has anything to do with Trump, I ain't taking it"
I can tell you from my perspective that Trump’s opinions on just about anything are vanishingly unimportant to me.
I disagree strongly with Trump. That doesn’t mean I feel any obligation whatsoever to mindlessly take positions in direct opposition to Trump.
I take positions on things independent of Trump, based on my own experiences and education.
I often find Trump on the other side of the issue of me. I wasn’t looking for which position he was going to take. I didn’t care. I just notice that whenever I take a position, he happens to be somewhere else in the room.
Which is why I disagree with Trump.
But I have never once in my life researched Donald Trump’s opinion on any issue before deciding where I stood on it.
I don’t think this is unique to me.
My decision to get vaccinated had took absolutely none of Trump’s opinion on the vaccine into account. At all. The only reason I’m even aware of his position is because the news decided to tell us.