Antivaxxers by country would be interesting. It probably relates to that number anyway. Levels of gullibility and other aspects such as just wont for no good reason really.
Well, Europe seems to have a higher number of antivaxers given the uptake, therefore by your own definition they are more gullible, so basically you're saying 'remainers' are more gullible and lean more toward antivaxing. Fair enough, I hadn't really thought about it before but maybe you're right given the number of NHS staff refusing vaccines.
Loony lefty remainer public sector = antivaxxer. Recent news headlines appear to back up your theory.