Inclusion Criteria

• For centers that will use fluconazole as the antifungal comparator
  • Age ≥ 3 months and < 21 years
• For centers that will use voriconazole as the antifungal comparator
  • Age ≥ 2 years and < 21 years
• The patient must be undergoing allogeneic HCT from any donor (including matched related) with any stem cell source for any underlying condition
• Patients must have a performance status corresponding to Eastern Cooperative Oncology Group (ECOG) scores of 0, 1 or 2
  • use Karnofsky for patients > 16 years of age and Lansky for patients ≤ 16 years of age
• Creatinine clearance or radioisotope glomerular filtration rate (GFR) ≥ 70 mL/min/1.73 m^2 OR a serum creatinine based on age/gender as follows
  • 0.4 mg/dL (1 month to < 6 months of age)
  • 0.5 mg/dL (6 months to < 1 year of age)
  • 0.6 mg/dL (1 to < 2 years of age)
  • 0.8 mg/dL (2 to < 6 years of age)
  • 1.0 mg/dL (6 to < 10 years of age)
  • 1.2 mg/dL (10 to < 13 years of age)
  • 1.5 mg/dL (male) or 1.4 mg/dL (female) (13 to < 16 years of age)
  • 1.7 mg/dL (male) or 1.4 mg/dL (female) ( ≥ 16 years of age)
• Total bilirubin < 2.5 mg/dL unless the increase in bilirubin is attributable to Gilbert's syndrome
• Serum glutamic oxaloacetic transaminase (SGOT) (aspartate aminotransferase [AST]) or serum glutamate pyruvate transaminase (SGPT) (alanine aminotransferase [ALT]) < 5 X upper limit of normal (ULN) for age
• All patients and/or their parents or legal guardians must sign a written informed consent
• All institutional, Food and Drug Administration (FDA), and National Cancer Institute (NCI) requirements for human studies must be met

Exclusion Criteria

• Within 90 days of enrollment
  • Patients with a proven or probable invasive mold infection
  • Patients with an incompletely treated invasive yeast infection 
• Patients with an elevated galactomannan level (≥ 0.5 index) within 30 days prior to time of enrollment must have a full evaluation for invasive aspergillosis (including a negative chest computed tomography [CT] scan) to be eligible for enrollment
• Patients receiving treatment for an IFI
• Patients with a history of echinocandin or azole hypersensitivity 
• Female patients of childbearing potential unless a negative pregnancy test result has been obtained
• Sexually active patients of reproductive potential unless they have agreed to use an effective contraceptive method for the duration of their study participation
• Lactating females unless they have agreed not to breastfeed their infants