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Updated: Sep 22, 2025

Trans-vivo Delayed Type Hypersensitivity Assay for Antigen Specific Regulation
Published on: May 2, 2013
Vaccine-induced prothrombotic immune thrombocytopenia without thrombosis may not require immune modulatory therapy: A
Chieh Min Benjamin Lai1, Agnes Y Y Lee1, Stephen B I Parkin1
1Division of Hematology University of British Columba Vancouver British Columbia Canada.
Background:
Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a rare complication of the ChAdOx1 nCoV-19 and Ad26.COV2.S COVID-19 vaccines. It presents most commonly with severe thrombocytopenia and thrombotic complications with extremely high D-dimer levels 5-30 days after vaccination. We report a patient who presented with mild thrombocytopenia and minimally elevated D-dimer levels without thrombosis, but who tested positive for antiplatelet factor 4 (PF4) platelet-activating antibodies on a PF4-enhanced serotonin-release assay.
Key Clinical Question:
Is immunomodulation necessary in patients who present without thrombosis?
Clinical Approach And Conclusions:
Treatment with rivaroxaban alone was followed by platelet normalization despite persistence of anti-PF4 antibodies. This case provides support that vaccination for COVID-19 can induce a broad, heterogeneous prothrombotic disorder characterized by anti-PF4 platelet-activating antibodies that shares features with classical heparin-induced thrombocytopenia (HIT) and autoimmune HIT syndromes and that immunomodulation may not be required in those without thrombosis.
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