I'll reiterate a point from my earlier post: You can't evaluate the statements by Biden or Harris in a vacuum. The reason they were saying they didn't trust Trump was not because they were engaging in wild conspiracy theories or trying to damage him politically. OK fine, I'm sure the latter played into their calculus, but the main reason was that Trump was going around telling everyone who would listen that he wanted a vaccine before the election. He would repeatedly say things like, "
“We’re gonna have a vaccine very soon. Maybe even before a special date. You know what date I’m talking about.”
When the FDA announced that the vaccine would not be approved before the election, Trump
threw a tantrum and accused the agency of making a political decision to hurt him (as
Trump's former ghostwriter has said, whenever Trump accuses someone of something, it's a good bet that he's projecting his own pathologies).
Now, I will concede that there's a fine line between calling out nakedly political behavior and undermining public confidence in the vaccine, and it's possible that Biden statement
@Max Power highlighted may have gotten a little too close to that line by assuming the FDA would go in the tank for Trump. Would have been better to say something like, "I hope that the professional scientists at the FDA recognize their duty to perform due diligence," etc. But for the most part, blaming Biden for undermining public confidence is like blaming the little kid in the fable for undermining confidence in the Emperor's state of dress. They were just pointing out the obvious.