... the original trial data submitted by AZ to the regulator (EMA) did not have enough data on over 65 year olds, so several countries recommended it only for younger people (such as health care workers). AZ later submitted data showing that the vaccine is efficacious in the older age group, so that restriction was lifted. But then a rare and dangerous clotting disorder that very predominantly affects the young was observed (this was not seen in the UK, the country who have given that vaccine the most, because they vaccinated the elderly with it). This is likely more than a statistical fluke because a mechanism by which these clots are linked to the vaccine has been made plausible. So now the risk profile suggests not giving it to the young. In any case the risk is, as correctly stated, very low and much lower than having severe or fatal Covid-19, from which AZ protects very well. So looks helter-skelter but it is actually rational, if hard to explain. And it remains rational to take that vaccine,