they're (scientists and doctors) so farged:
if they say it's nothing, and carry on jabbing people, they invite republican castigation for ignoring the science/being hypocrites, and get to watch people decide that Trump was right and it's all a hoax
if they shut it down over fewer than one case in a million having some problem, tens of thousand more will get sick and hundreds more will die, minimum...and oh, yeah, they'll be castigated by the Republicans for making it harder for people to get the shot