B-Cell Lymphoblastic Leukemia

This is a Phase 2 Study is to determine the efficacy and safety rate of B-Cell Acute Lymphoblastic Leukemia (B-ALL) participants in remission with minimal residual disease (MRD) after KTE-X19 CAR T-cell therapy

The goal of this observational study is to establish a clear vaccination protocol for pediatric patients (less than 21 years old) who have received treatment for B-cell Acute Lymphoblastic Leukemia/Lymphoma. The main study aims are: * Evaluate the persistence of protective immunity to routine childhood vaccinations in participants with B-ALL/Ly who have received blinatumomab. * To determine whether revaccination in participants with non-protective titers leads to restored humoral immunity. Researchers will compare results from participants who have received immunotherapy to those who have not received immunotherapy to see if immunotherapy versus other chemotherapeutic drugs adversely affect the protective immunity acquired through vaccination.

The goal of this clinical trial is to evaluate the efficacy of Blinatumomab in pediatric patient with newly diagnosed acute B-Lymphoblastic leukemia with poor response to early chemotherapy, i.e. day 19 MRD ≥ 0.1% (low-risk) or day 19 MRD ≥ 0.01% (intermediate-risk). The main question is: • If the flow cytometric MRD negative (\<0.01%) rate and the NGS- MRD negative (\<0.0001%) rate at the end of induction for patients received Blinatumomab will be superior to historical control (D46MRD in the CCCG-ALL2020 protocol). Participants will: * Take 14 days full dose Blinatumomab; * With bone marrow evaluated before and after Blinatumomab treatment.