ABSTRACT: Vaccine-induced immune thrombotic thrombocytopenia (VITT) has emerged as a rare side effect of adenoviral vector-based vaccines against coronavirus disease 2019 (COVID-19), and is most frequently reported after use of the Vaxzevria (AstraZeneca) vaccine. This report describes a case of severe thrombocytopenia associated with massive pulmonary embolism and portal vein thrombosis occurring 13 days after the administration of the single-dose adenoviral vector-based vaccine Ad26.COV2.S (Janssen Vaccines). Based on early clinical suspicion, the patient quickly received treatment with corticosteroids and intravenous immunoglobulin, followed by a rapid increase in platelet count that allowed timely administration of full-dose anticoagulation. Treatment with intravenous immunoglobulin, however, could mask the ability of anti-platelet factor 4-heparin antibodies to bind and activate platelets in the presence of heparin, leading to false-negative results on the immunoassay functional test. Therefore, if VITT is suspected, blood samples for diagnostic confirmation should be collected prior to any treatment to improve diagnostic performance.
Full Text Finder