LAUSR

Patients with β -thalassemia show 5-fold increase in age-standardized lethality due to SARS-CoV-2 infection, representing a high-risk population compared with age- and sex-matched healthy subjects. 1 Vaccination against SARS-CoV-2 is crucial to reduce mortality and morbidity of frail patients. 2 Up to now, limited data have been available on the responses of patients with β -thalassemia immunized with anti – SARS-CoV-2 mRNA vaccines. 3 The syndrome of vaccine-induced immune thrombotic thrombocytopenia (VITT) is a rare thromboembolic complication of adenoviral-vectored severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines ChAdOx1 nCoV-19 (AstraZeneca) and Ad26.COV2.S (Janssen/Johnson & Johnson) mediated by antibodies directed against platelet factor 4 (PF4). 1-5 The mechanisms by which the adenoviral DNA vectors break immune tolerance to PF4 and trigger B-cell clonal expansion and secretion of anti-PF4 immunoglobulin Gs (IgGs) are under intense investigation and likely involve formation of immuno-genic complexes of PF4 with vaccine components in a proin- fl ammatory setting. 6 Pathogenic anti-PF4 IgGs subsequently form circulating immune complexes with PF4 tetramers, which are thought to drive thrombotic events by Fc γ receptor IIa – dependent platelet activation and to activate granulocytes to release procoagulant neutrophil extracellular traps. 6-8 Serum anti-PF4 antibodies are mostly transient and