Immune Function and Response to Vaccination After Cancer Therapy in Pediatric Patients

Patients will have lab evaluations for immune function at baseline, 3, 6, 9 and 24 months post completion of treatment. At 3 months off therapy, patients with abnormal vaccine antibody titers will be randomized to receive either single booster vaccines or to begin a full revaccination series that models post-hematopoietic stem cell transplant vaccination strategies.