A Second Infusion (Early Reinfusion) of Tisagenlecleucel in Children and Young Adults With B-Cell Acute Lymphoblastic Leukemia(B-ALL)

Inclusion Criteria: * Patients with R/R B-ALL who have received commercial tisagenlecleucel and have (an) additional dose(s) available for early reinfusion * History of CD19 expressing (in peripheral blood or bone marrow by flow cytometry) BALL prior to tisagenlecleucel infusion * Peripheral blood B-cell aplasia (BCA) within 14 days prior to reinfusion (See section 13.8: B-cell aplasia will be defined as peripheral blood (PB) absolute B lymphocyte count ≤ 50/μL. If BCA evaluation is repeated at any timepoint prior to reinfusion, it must be negative to proceed with reinfusion * Minimal residual disease negative complete remission (CR/CRi) in bone marrow within 14 days prior to reinfusion, including resolution of extramedullary disease * Patients with tisagenlecleucel that is deemed out of specification (OOS) will be permitted on this protocol if the reason for OOS is deemed to not impact the toxicity and efficacy profile of CAR T cell therapy °Reasons for product being OOS include cell viability \< 80%, total nucleated cell count \<2 × 10\^9 in leukapheresis product, failed interferon-γ release assay, leukapheresis product collected \>9 months prior, and determination of residual beads \>50 beads per 3 × 10\^6 cells * Patients age: \< 26 years at time of first tisagenlecleucel order placement * Recovered from severe toxicities following initial dose of tisagenlecleucel * CRS * Neurotoxicity/ICANS * Adequate organ function at time of treatment is required and is defined: * Hepatic: Serum bilirubin ≤ 2 mg/dL, unless benign congenital hyperbilirubinemia * Hepatic: AST and ALT \< 5x the upper limit of normal for age, unless thought to be disease-related * Renal: Serum creatinine \<1.5x normal for age. If serum creatinine is outside the normal range, then CrCl \> 60 mL/min/1.73m2 (calculated or estimated) or GFR (mL/min/1.72m2 ) \>55% of predicted normal for age Age Mean GFR +/-SD (mL/min/1.73 m2) * 1 week 40.6 + / - 14.8 * 2 - 8 weeks 65.8 + / - 24.8 * \> 8 weeks 95.7 +/- 21.7 * 2 - 12 years 133 +/- 27 * 13 - 21 years (males) 140 +/- 30 * 13 - 21 years (females) 126.0 + / - 22.0 Abbreviations: GFR, glomerular filtration rate; SD, standard deviation. Greater than 2 years old: Normal GFR is 100 mL/ min. Infants: GFR must be corrected for body surface area. * Cardiac: LVEF ≥ 50% by multi-gated acquisition scan (MUGA), resting echocardiogram, or cardiac magnetic resonance imaging (MRI) within 6 weeks of screening * Pulmonary: Oxygen saturation as recorded by pulse oximetry of ≥ 90% on room air * Adequate performance status: * Age ≥ 16 years: ECOG ≤ 1 or Karnofsky \> 60% at treatment * Age \< 16 years: Lansky \> 60% at treatment * Patient must be enrolled on institutional CIBMTR reporting protocol for immune effector cells (IEC)/CAR T cells * Each patient must be willing to participate as a research subject, and patient or legal guardian must sign an informed consent form, along with patient assent if between 7 to 17 years of age. Legally authorized representatives of adult patients with impaired decision-making capacity will also be able to sign consent. Exclusion Criteria: * Greater than 60 days from first tisagenlecleucel infusion * Ongoing severe toxicities from initial CAR T cell infusion * Received non-standard lymphodepleting chemotherapy (LDC) prior to initial tisagenlecleucel dose * Standard LDC is defined as: * Fludarabine 30mg/m\^2/dose x 4 doses * Cyclophosphamide 500mg/m\^2/dose x 2 doses * Loss of BCA at any timepoint prior to reinfusion * Clinically significant active infection confirmed by clinical evidence, imaging, or positive laboratory tests (e.g., blood cultures, PCR for DNA/RNA, etc.) * Patient/parent/guardian unable to give informed consent or unable to comply with the treatment protocol * Pregnant or lactating women; women of child-bearing potential, defined as all women physiologically capable of becoming pregnant, unless they are using highly effective methods of contraception while taking study treatment and for at least 12 months after the tisagenlecleucel infusion and until CAR T-cells are no longer present by flow cytometry on two consecutive tests. * Sexually active males, unless they are willing to use a condom during intercourse while taking study treatment and for at least 12 months after the tisagenlecleucel infusion and until CAR T-cells are no longer present by flow cytometry on two consecutive tests. * Other uncontrolled, symptomatic, intercurrent illness including but not limited to infection, psychiatric illness, or social situations that would limit compliance with study requirements or in the opinion of the PI would pose an unacceptable risk to the subject * Any other issue which, in the opinion of the treating physician, would make the patient ineligible for the study