I’m not sure if there are increased risks if you already have clotting issues, but it is one of the questions on the health screening you have to complete before having the vaccine.
My husband had his a month or so ago. Vaccination centre had no one there, so were seeing anyone who wanted it (AZ) regardless of category. I’m getting mine tomorrow (Pfizer) as 1b category. Was booked in already - not doing it because of the Melbourne outbreak.