B-cell Childhood Acute Lymphoblastic Leukemia

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.

This trial will assess the feasibility of alpha/beta T-cell and B-cell depleted allogeneic hematopoietic cell transplantation (HCT) followed by blinatumomab therapy for high-risk B cell acute lymphoblastic leukemia (ALL) as a means of reducing rates of subsequent relapse and improving survival, while also minimizing treatment-related morbidity/ mortality and late effects. The conditioning regimens will be dependent on the patient's minimal residual disease (MRD) status prior to HCT using high throughput sequencing.