Phase II Trial of a Bivalent Vaccine With the Immunological Adjuvant OPT-821 (QS-21), in Combination With Randomization of Oral β-glucan, for High-Risk Neuroblastoma

Inclusion Criteria: * Diagnosis of NB as defined by international criteria,102 i.e., histopathology (confirmed by the MSK Department of Pathology) or BM metastases plus high urine catecholamine levels, or positivity in MIBG scan. * HR-NB as defined by risk-related treatment guidelines and international criteria,102 i.e., metastatic/non-localized disease with MYCN amplification (any age), metastatic disease \>18 months old, MYCN-amplified localized disease (any age), or disease resistant to standard chemotherapy. * HR-NB (as defined above) and in 1) first CR at ≥ 6 months from initiation of immunotherapy using anti-GD2 antibody, or 2) second or subsequent CR (achieved after treatment for PD). CR is defined according to the International Neuroblastoma Response Criteria. Patients with positive MIBG scan but negative FDG-PET scan, and CR in BM, are eligible. * Patients with grade 3 toxicities or less using the Common Toxicity Criteria (Version 5.0) developed by the National Cancer Institute of the USA (CTCAE v5.0) related to hematologic, cardiac, neurological, pulmonary, renal, hepatic or gastrointestinal function as determined by blood tests or physical exam. Plus: * Absolute neutrophil count (ANC) ≥ 500/mcl * Absolute lymphocyte count ≥ 500/mcl * \>21 and \<180 days between completion of systemic therapy and 1st vaccination. * A negative pregnancy test is required for patients with child-bearing capability * Signed informed consent indicating awareness of the investigational nature of this program. Exclusion Criteria: * Patients with grade 4 hematologic, cardiac, neurological, pulmonary, renal, hepatic or gastrointestinal function as determined by blood tests or physical exam, using the Common Toxicity Criteria (Version 5.0) developed by the National Cancer Institute of the USA. * History of allergy to KLH, QS-21, OPT-821, or glucan * Prior treatment with this vaccine. * Active life-threatening infection requiring systemic therapy. * Inability to comply with protocol requirements.