ChAdOx1 nCoV-19 vaccine-associated thrombocytopenia: three cases of immune thrombocytopenia after 107 720 doses of ChAdOx1 vaccination in Thailand.

We reported three cases of immune thrombocytopenia (ITP) that developed within 6 weeks after ChAdOx1 nCoV-19 vaccination. Antiplatelet factor 4 antibodies were undetectable in all three cases. Therefore, vaccine-induced immune thrombotic thrombocytopenia was very unlikely. Other potential causes of thrombocytopenia were excluded. Their clinical presentations, severity of thrombocytopenia and outcomes were varied. Only one ITP case, an 80-year-old man, received ITP treatments and achieved complete response after 2 weeks of eltrombopag. An 84-year-old man had spontaneous complete remission, and a 55-year-old woman had partial platelet recovery without ITP treatments. Among 107 720 Thais administered the ChAdOx1 vaccine between 16 March and 10 May 2021, these three ITP cases resulted in an estimated risk of ITP of at least one per 36 000 doses, which was approximately similar to the risk of ITP after measles-mumps-rubella immunization. This raises the concern of an increased risk of ITP after ChAdOx1 vaccination.

Incidence and risk factors of relapses in idiopathic autoimmune hemolytic anemia.

BACKGROUND: Patients with idiopathic autoimmune hemolytic anemia (AIHA) of warm antibody type usually respond to corticosteroid therapy. However a proportion of patients will have disease relapse after steroid-induced remission. OBJECTIVE: To assess the incidence and the possible risk factors of the relapse in a cohort of patients with idiopathic AIHA. MATERIAL AND METHOD: We conducted a retrospective and prospective study of 34 idiopathic AIHA patients regularly followed at the Division of Hematology during January 1973 to December 2006. The medical records were reviewed for active hemolytic events and relapses, episodes of infections, pattern of corticosteroids administration and tapering. Types and subtypes of autoantibodies were studied by column agglutination test (the "gel test"). RESULTS: One patient with cold agglutinin disease was excluded, leaving a total of 33 patients (24 with warm type, 9 with mixed warm and cold type AIHA) in the study. The incidence of relapse was 1.157 episodes/person/year. The mean duration of relapse after remission was 23 months. Episodes of recurrent hemolysis were more frequent when corticosteroid administration was tapered from high to low dose (10 mg/day of prednisolone) within two months compared with a longer than two-month tapering (38 vs. 11 episodes; p < 0.01). In addition patients receiving continuing low dose of corticosteroids (< or = 10 mg/day of prednisolone) for > 6 months had lower incidence of relapse and longer duration of remission than those with discontinuing the medication within 6 months (0.443 vs. 1.911 episodes/person/year, p < 0.01; 37.4 vs. 10.6 months, p < 0.01). Episodes of recurrent hemolysis were more frequently observed in patients with events of infection than those without infections (mean 7.69 vs. 2.81, p = 0.032). Types and subtypes of autoantibodies did not seem to influence relapse in AIHA. CONCLUSION: Short duration of maintenance and rapid tapering of corticosteroids and infections are possible risk factors of relapses/recurrent hemolysis in idiopathic AIHA.