https://sebastianrushworth.com/2021/04/17/is-the-astra-zeneca-vaccine-killing-people/

Great writeup on why it these blood clots were 1) so alarming, 2) definitely caused by Astra Zeneca.

"So four people out of 132,000 who received the Astra-Zeneca vaccine developed the normally exceedingly rare combination of thrombocytopenia with cerebral venous sinus thrombosis. All had received the Astra-Zeneca vaccine seven to ten days earlier."

"It’s so uncommon that only a handful of cases have been reported in the entire medical literature. Up to now, that is."