COVID‐19: Vaccine‐induced immune thrombotic thrombocytopenia

In late February 2021, a prothrombotic syndrome was encountered for the first time in some of the recipients of ChAdOx1 CoV‐19 vaccine (AstraZeneca, University of Oxford, and Serum Institute of India). Since the hallmark of this syndrome is the development of thrombocytopenia and/or thrombosis between 4 and 42 days after receiving a COVID‐19 vaccine, it was named vaccine‐induced immune thrombotic thrombocytopenia (VITT). Other names include “vaccine‐induced prothrombotic immune thrombocytopenia” and “thrombosis with thrombocytopenia syndrome” by the Centers for Disease Control and the Food and Drug Administration (FDA). VITT appears similar to heparin‐induced thrombocytopenia in that “platelet activating” autoantibodies are produced in both these conditions due to prior exposure of COVID‐19 vaccine and heparin respectively, in turn causing thrombotic complications and consumptive thrombocytopenia. In this article, recent advances in the understanding of pathobiology, clinical features, investigative work‐up, and management of VITT are reviewed.