It could be, though as I mentioned in another comment these results don't reflect my own experience in my social circles, where if anything having (or working-t

It could be, though as I mentioned in another comment these results don't reflect my own experience in my social circles, where if anything having (or working-towards) a PhD correlates with being more trusting of the vaccine (with the caveat of my sample being skewed towards experimental sciences and biology in particular). In any case, after reading other comments mentioning that the data is self-reported, I find it much more believable that many vaccine-hesitants have falsely claimed to have a PhD. That would explain why only the purported "PhD" group is disproportionately hesitant. If it was a real effect you would expect at least some increase in hesitancy in people with Master's, who may well be on their way towards a PhD.