In December 2020 the Israeli Health Ministry began a mass vaccination campaign with the BNT162b2 vaccine. This was an important step in overcoming the severe acute respiratory syndrome corona virus 2 (SARS‐CoV‐2) pandemic. Autoimmune phenomenon have been described after receiving vaccinations. Here we describe a case series of patients who developed acquired Thrombotic Thrombocytopenic Purpura, a rare autoimmune disease, within several days of receiving the BNT162b2 vaccine. A disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13(ADAMTS13) activity should be evaluated in patients with history of aTTP before and after any vaccination, especially the SARS‐CoV‐2 vaccination, and immunosuppression treatment should be considered before vaccination in cases of low ADAMTS13 activity. Patients should be closely monitored after the vaccine for clinical situation and laboratory data. Post vaccination thrombocytopenia assessment should include immune thrombocytopenic purpura, vaccine‐induced immune thrombotic thrombocytopenia and acquired thrombotic thrombocytopenic purpura.

Acute myeloid leukemia (AML) relapse is often associated with a poor outcome, especially after allogeneic stem cell transplantation (Allo-SCT). In patients relapsing early after SCT treatment, options are further limited by the fear for increased toxicity. We report our experience with ARA-C and gemtuzumab ozogamicin (GO) combination in relapsed post-SCT AML patients. Therapy consisted of ARA-C (1 gr/m(2)) for 4 days followed by one dose of GO 9 mg/m(2) on day 5 and was supported by donor stem cells when possible. Responding patients not developing graft versus host disease (GVHD) were eligible for immunotherapy with donor lymphocyte infusion (DLI) or a second Allo-SCT. Sixteen patients, median age 53 years (range 31-63), are included in this analysis. Patients underwent SCT for high-risk AML (n = 11) or AML relapse (n = 5), and 81 % had an early post-SCT relapse. Responses were achieved in 60 % of evaluable patients (CR-5 CRp-4). Median probabilities of survival (OS) and event-free survival (EFS) in the entire cohort, responding and non-responding patients were 103 and 76 days, 183 and 97 days, and 79 and 16 days, respectively. At 1-year follow-up, 25 % of patients were alive; however, all had relapse. Treatment resulted in grade 3-4 neutropenia and thrombocytopenia in all patients, and 27 % each had grade 3-4 hyperbilirubinemia or elevation of liver enzymes. One patient died during treatment due to intracranial hemorrhage. Of the six patients proceeding to second SCT or receiving DLI, three patients developed mild veno-occlusive disease (VOD). Combination therapy with ARA-C and GO after SCT results in short-term disease control and limited toxicity and could be considered for patients who are candidates for further immunotherapy.