I recently read an article which suggested the clotting was caused by the anti bodies these people created, and as such it was person specific and not vaccine specific.
The article seemed to imply that if these people had any vaccine, or in fact caught covid, they were at high risk of clotting.
We know already that covid can have a strange effect on the blood. There have been several cases of young people clotting and having strokes from covid.
Maybe if they can identify the risk group these people can be vaccinated under observation.