Inclusion Criteria:

• 2 to < 18 years of age, inclusive (at the time of the first administration of study intervention at Week I-0) with a body weight ≥ 10 kg.
• Medically stable on the basis of physical examination, medical history, and vital signs performed at screening. Any abnormalities must be consistent with the underlying illness in the study population and this determination must be recorded in the participant's source documents and initialed by the investigator.
• Medically stable on the basis of clinical laboratory tests performed at screening. If the results of the serum chemistry panel including liver tests, other specific tests, blood coagulation, hematology, or urinalysis are outside the normal reference ranges, the participant may be included only if the investigator judges the abnormalities or deviations from normal to be not clinically significant or to be appropriate and reasonable for the population under study. This determination must be recorded in the participant's source documents and initialed by the investigator.

Exclusion Criteria:

• Has complications of Crohn’s disease such as symptomatic strictures or stenosis, short gut syndrome, or any other manifestation that might be anticipated to require surgery, that could preclude the use of the PCDAI to assess response to therapy or would possibly confound the ability to assess the effect of treatment with ustekinumab.
• Currently has or is suspected to have an abscess. Recent cutaneous and perianal abscesses are not exclusionary if drained and adequately treated at least 3 weeks prior to baseline, or 8 weeks prior to baseline for intra-abdominal abscesses, provided that there is no anticipated need for any further surgery. Participants with active fistulas may be included if there is no anticipation of a need for surgery and there are currently no abscesses identified.
• Has had any kind of bowel resection within 6 months or any other intra-abdominal surgery within 3 months prior to Week I-0.
• Has a draining (i.e., functioning) stoma or ostomy.
• Have Crohn’s disease or fistulizing Crohn’s disease of at least 3 months duration, with active colitis, ileitis, or ileocolitis, confirmed at any time in the past by endoscopy and histology.
• Must have moderately to severely active Crohn’s disease (as defined by a baseline PCDAI score > 30) AND at least one of the following:
  • An abnormal CRP (> 0.3 mg/dL or 3.0 mg/L at screening); OR
  • Fecal calprotectin of ≥ 250 mg/kg or ≥ 250 µg/g at screening; OR
  • Ileocolonoscopy with evidence of active Crohn’s disease (defined as ulcerations in the ileum and/or colon) during screening into this study including at the baseline visit.