So the reason given by "them" is that the particular vaccine they withdrew has been superseded by other releases and isn't selling anymore. They had admitted to this thrombosis issues in 2-3 of 100,000 people.
I realise the usual response would be, "Well they would say that; it's big Pharma/media they lie and they lie and they lie..." but if they were still selling hundreds of thousands of units of this every month do you really think they'd withdraw it because of that incident rate?
Their track record of putting profit above people suggests not, so the framing of "Astrazenica pulls vaccine because of side effect" is really "Astrazenica pulls vaccine because they aren't making any money off it".
This doesn't remove the fact that there is a side effect and whatever they said about that earlier (I don't follow this closely enough to be able to cite it) but it is definitely a case of "the framing changes the story".