PF4 and Thrombocytopenia: Indeed, Greinacher and colleagues, Schultz and colleagues, and Scully and colleagues reported the detection of platelet-activating anti-PF4 antibodies in sera of patients suffering from unusual thrombotic events associated with thrombocytopenia within 4 to 16 days after injection of the ChAdOx1 nCoV-19 vaccine [44–46].