VACCINE-INDUCED IMMUNE THROMBOTIC THROMBOCYTOPENIA (VITT) BY A THIRD DOSE OF CHADOX1 NCOV-19 (ASTRAZENECA) AFTER BNT162B2 (PFIZER–BIONTECH)

Abstract

An atypical case of VITT was described resulting from a vaccination schedule where the third booster with ChAdOx1 nCoV-19 (AstraZeneca) was administered. The patient received a complete vaccination schedule with two doses of Pfizer-BioNTech (BNT162b2) without any complications before the third dose. However, the patient has developed an infrequent yet extreme prothrombotic; hypercoagulable state caused by platelet-activating anti-Platelet Factor 4 (PF4) antibodies. This phenomenon is typically triggered by the proximate administration of an adenoviral vector vaccine against COVID-19. The patient's symptoms began ten days after taking the third dose of the ChAdOx1 nCoV-19 vaccine (AstraZeneca). His main complaints when hospitalized were severe headaches and right abdominal pain. The blood tests and MRI scan imaging findings were very characteristic of VITT, and a rare cerebral venous sinus thrombosis was found. Also, a markedly elevated D-dimer and strong positive PF4-dependent enzyme-immunoassay test results were documented. Due to discerning clinical suspicion, this patient was rapidly treated with immunoglobulin infusion for two days and oral steroids for three days. Subsequently, he was anticoagulated with the new oral anticoagulant edoxaban after platelet numbers recovery. In a few days, platelets normalized, and D-dimer levels decreased, while anti- PF4-dependent enzyme-immunoassay test results showed a slow decline. He was discharged taking oral edoxaban without any sequeal.