A Study to Investigate the Safety and Efficacy of Fidaxomicin (Oral Suspension or Tablets) and Vancomycin (Oral Liquid or Capsules) in Pediatric Subjects With Clostridium Difficile-associated Diarrhea (CDAD)

Inclusion Criteria: * Subject is diagnosed with CDAD according to local diagnostic criteria. As a minimum there must be positive detection, within 72 hours prior to randomization, of either toxin A and/or toxin B in stool or positive detection of toxigenic C. difficile in stool and: * Subject from Birth to \< 2 years: watery diarrhea in the 24 hours prior to screening. * Subject ≥ 2 years to \< 18 years: ≥ 3 unformed bowel movements in the 24 hours prior to screening. * Male and female subjects aged from birth to \< 18 years: Note that in the United States of America subjects can only be included if aged ≥ 6 months to \< 18 years. * For subjects \< 5 years: Negative rotavirus test. * Female subject of childbearing potential: * must have a negative urine pregnancy test at Screening, and * must abstain from sexual activity for the duration of the study, or * must use two forms of birth control (at least one of which must be a barrier method) starting at Screening and throughout the study period and for 28 days after the final study drug administration. * Female subject must not be breastfeeding at Screening or during the study period, and for 28 days after the final study drug administration. * Female subject must not donate ova starting at Screening and throughout the study period, and for 28 days after the final study drug administration. * Subject agrees not to participate in another interventional study while in the study (with the exception of studies as des…