New-Onset Antibodies to Platelet Factor 4 Following Liver Transplantation From a Donor With Vaccine-Induced Thrombotic Thrombocytopenia

Since February 2021, some recipients of ChAdOx1 nCov-19 or Ad26.COV2.S vaccines have been observed to have developed antibodies against platelet factor-4 (PF4)/polyanion complexes, thrombocytopenia and thrombosis, a severe condition resembling Heparin-Induced Thrombocytopenia (HIT) (1). The syndrome has been termed "Vaccine-Induced Immune Thrombotic Thrombocytopenia (VITT)" or "Thrombosis with Thrombocytopenia Syndrome (TTS)" (6).