An underlying syndrome denoted “vaccine-induced immune thrombotic thrombocytopenia” (VITT) [4, 5] or “thrombosis with thrombocytopenia syndrome” (TTS) [6] was described, consisting of thrombosis, thrombocytopenia and platelet-activating antibodies to platelet factor 4–polyanion complexes. This evidence concerns the gene PF4 and deep vein thrombosis.