Heterogeneity of Vaccine-Induced Immune Thrombotic Thrombocytopenia after ChAdOx1 nCoV-19 Vaccination and Safety of Second Vaccination with BNT162b2

Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a rare side effect of two adenoviral vector vaccines, ChAdOx1 nCoV-19 (AstraZeneca) and Ad26.COV2.S (Johnson & Johnson/Janssen); it is caused by platelet-activating immunoglobulin G (IgG) that recognizes platelet factor 4 (PF4), as shown by positive testing by PF4/heparin-enzyme-linked immunosorbent assay (PF4-H-ELISA) in combination with PF4-enhanced washed platelet activation assays...