Thrombosis and Thrombocytopenia after ChAdOx1 nCoV-19 Vaccination

This brief report presents five cases of vaccine-induced immune thrombotic thrombocytopenia (VITT) in previously healthy healthcare workers aged 32 to 54, who developed thrombosis in atypical sites and severe thrombocytopenia 7 to 10 days after receiving the first dose of the ChAdOx1 nCoV-19 (AstraZeneca) vaccine. Thromboses included cerebral venous sinus, portal vein, and splanchnic vein involvement; three patients died due to intracerebral hemorrhage. All tested strongly positive for anti–platelet factor 4 (PF4) antibodies by ELISA, resembling autoimmune heparin-induced thrombocytopenia despite no prior heparin exposure. Platelet aggregation testing revealed activation in the absence of heparin in most cases. Treatment included intravenous immune globulin and corticosteroids, with platelet recovery in surviving patients. The authors propose VITT as a rare but serious immune-mediated adverse event post-vaccination and recommend PF4 ELISA testing and functional platelet assays for diagnosis. Risk–benefit analysis remains essential for vaccine safety policy and clinical vigilance.

This brief report presents five cases of vaccine-induced immune thrombotic thrombocytopenia (VITT) in previously healthy healthcare workers aged 32 to 54, who developed thrombosis in atypical sites and severe thrombocytopenia 7 to 10 days after receiving the first dose of the ChAdOx1 nCoV-19 (AstraZeneca) vaccine. Thromboses included cerebral venous sinus, portal vein, and splanchnic vein involvement; three patients died due to intracerebral hemorrhage. All tested strongly positive for anti–platelet factor 4 (PF4) antibodies by ELISA, resembling autoimmune heparin-induced thrombocytopenia despite no prior heparin exposure. Platelet aggregation testing revealed activation in the absence of heparin in most cases. Treatment included intravenous immune globulin and corticosteroids, with platelet recovery in surviving patients. The authors propose VITT as a rare but serious immune-mediated adverse event post-vaccination and recommend PF4 ELISA testing and functional platelet assays for diagnosis. Risk–benefit analysis remains essential for vaccine safety policy and clinical vigilance.