Correction: there are a bunch of screenshots and videos about people saying they would not trust a vaccine just because President Trump said so. Given all of the awful advice that was common from the then-president (e.g.: hydroxychloroquine), that was perfectly reasonable.

You can probably find exceptions, but the widely spread examples I am aware of all then went on to talk about believing it when it came from the CDC and other authorities.

I would argue that there has been little flipping. Those who were not going to get the vaccine under President Trump are also not going to get it under President Biden. The recent "boo"ing of former President Trump at his recent rally when he recommended people get vaccines is just the latest evidence of that.