The spectrum of platelet-activating anti-PF4 disorders expanded in 2021 with the recognition of VITT, a platelet-activating, prothrombotic disorder caused by anti-PF4 antibodies that are rarely formed following COVID-19 vaccination with ChAdOx1 nCoV-19 [[6], [7], [8]] or Ad26.COV2.S [9], both engineered as adenoviral vector vaccines. The gene discussed is PF4; the disease is COVID-19.