That's right. There is no authority principle in science, and a representative of an institution/agency of US saying that something "should be strong enough to"

That's right. There is no authority principle in science, and a representative of an institution/agency of US saying that something "should be strong enough to", does not mean that the "science" said "it is going to be like this", especially given the so many unknown variables that come into play. That is one of the common misunderstandings. People make mistakes, and we have plenty of people with credentials that made bad predictions. The vaccines worked as intended, thought. The criticism should be targeted elsewhere. My personal opinion is that in many countries there hasn't been a good communication, and being an expert on a field doesn't qualify someone to be good at explaining things to the wide public.