Pathologic Antibodies to Platelet Factor 4 after ChAdOx1 nCoV-19 Vaccination

16 April 2021, New England Journal of Medicine


Report of findings in 23 patients who presented with thrombosis and thrombocytopenia 6 to 24 days after receiving the first dose of the ChAdOx1 nCoV-19 vaccine (AstraZeneca). Of the 22 patients who presented with thrombosis, 13 had clinical features consistent with cerebral venous thrombosis (1 with concurrent acute portal vein thrombosis and pulmonary embolism), 4 had pulmonary embolism (1 with concurrent deep venous thrombosis), 1 had deep venous thrombosis and bilateral adrenal hemorrhage, 2 had an ischemic stroke affecting the middle cerebral artery territory, and 2 had portal vein thrombosis (1 with concurrent acute myocardial infarction and 1 with evidence of concurrent acute aortic thrombosis on imaging). Additional thrombosis events associated with progression occurred in patients who received platelet transfusions or heparin-based therapy at presentation. Within the entire cohort, 7 patients (30%) died. Results of a postmortem evaluation, available for 1 patient, showed evidence of thrombosis in many small vessels, especially vessels in the lungs and intestine, cerebral veins, and venous sinuses, as well as evidence of extensive intracerebral hemorrhage.

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