Lessons from vaccine-induced immune thrombotic thrombocytopenia

Adenoviral vector vaccines are effective against SARS-CoV-2 but have been associated with a rare side effect termed vaccine-induced immune thrombotic thrombocytopenia (VITT). Here, we discuss our understanding of how vaccine-induced antibodies to platelet factor 4 (PF4) form immune complexes that activate platelets and trigger the thrombotic events seen in VITT. Here, John Kelton and colleagues provide an overview of vaccine-induced immune thrombotic thrombocytopenia (VITT), a very rare complication that has been observed following vaccination with adenoviral vector-based COVID-19 vaccines.