Back on the blood clotting risk thing, I found
this paper from the Winton Centre for Risk and Evidence Communication at Cambridge University which is a very good discussion of the risks and benefits for the AZ vaccine in different age groups depending on the prevalence of COVID infections in the population.
The top figure is the standout one. At current infection rates, the risk of blood clots of the type seen in vaccinated patients in the 20-29 year age range is higher than the risk of ICU admission due to COVID.
If infection rates rise, then the risk/benefit swings towards vaccination but of course we want to go towards lower rates...