Administration of the COVID-19 vaccine ChAdOx1 nCOV-19 has been associated with cases of Vaccine-Induced Prothrombotic Immune Thrombocytopenia (VIPIT).
Patient selection: status post administration of ChAdOx1 nCoV-19 vaccine (AstraZeneca)
Mechanism: antibodies causing activation of the platelet Fc receptor, resembling HIT
Features:
(1) onset 4 to 16 days after vaccination
(2) variable thrombosis at unusual sites (cerebral vein, splanchnic vein)
(3) thrombocytopenia
(4) positivity in the anti-platelet factor 4 immunoassay
(5) response to high-dose intravenous immunoglobulin (IVIG) and non-heparin anticoagulation
(6) exclusion of other causes such as heparin exposure
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