It wasn't "science" which was changing its mind though – "science" doesn't have a mind – it was the public health authorities. The same authorities would change their recommendations over time, and authorities in different countries were making different recommendations at the same time. In part, this was due to differences in circumstances (across both time and space) around the severity of the pandemic, availability of vaccines, hospital resources, etc. But, another factor was that, despite (at any given point in time) all having largely the same scientific evidence, they sometimes interpreted it in different ways, drew different conclusions from it, differed in the weight they decided to give to individual pieces of evidence, etc. It is legitimate for people to question whether they were interpreting the available evidence correctly – and this is not just a matter of hindsight, even at the time, there were qualified professionals who disagreed with their judgements.
I think this frequent conflation of "science" with "public health authority interpretations of science" is rather misguided – and it isn't just "anti-vax" people who commit that conflation, many "pro-vax" people do the exact same thing. I've always been supportive of vaccination – indeed, I have all my recommended doses of COVID-19 vaccine – but I think the excessive rhetoric which some people use against those who express doubts has been very harmful – it has actually been a major unnecessary setback in the cause of encouraging vaccination.
