Efficacy Study of Blinatumomab Clean Up Early Residual Disease for Newly Diagnosed Pediatric B Lymphoblastic Leukemia

Inclusion Criteria: * Age older than 1 month to younger than 18 years. * Diagnosis of acute lymphoblastic leukemia by bone marrow morphology. * Immunophenotyping: acute B-lymphoblastic leukemia; * Meet one of the following situations: A. Provisional low-risk: D19MRD ≥ 0.1%; B. Provisional intermediate-risk: D19MRD ≥ 0.01%; * Subjects in the sytudy group or their guardians must be able to understand and accept the informed consent approved by the Ethics Committee Exclusion Criteria: * sIgM+; * ALL evolved from chronic myeloid leukemia (CML); * Down's syndrome, or major congenital or hereditary disease with organ dysfunction; * Other secondary leukemias; * CNS involvement; * History of epilepsy; or convulsions within the last month; * Known underlying congenital immunodeficiency or metabolic disease; * Congenital heart disease with cardiac insufficiency; * Treated with glucocorticoids for ≥14 days, or ABL kinase inhibitors for \> 7 days within one month before enrollment, or any chemotherapy or radiotherapy within 3 months before enrollment (except for emergency radiotherapy to relieve airway compression); * Initial diagnosis of high risk; * D46MRD ≥1%.