A Study of Ustekinumab in Pediatric Participants With Moderately to Severely Active Ulcerative Colitis (UC)

Inclusion Criteria: * 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 acknowledged by the investigator * Must have had UC diagnosed prior to screening * Have moderately to severely active UC, defined as a baseline Mayo score of 6 through 12, inclusive, with a screening Mayo endoscopy subscore greater than or equal to (\>=) 2 as determined by a central review of the video of the endoscopy * A participant who has had extensive colitis for \>= 8 years, or disease limited to the left side of the colon for \>= 10 years, must: a) have had a full colonoscopy to assess for the presence of dysplasia within 1 year before the first administration of study intervention or b) have a full colonoscopy with surveillance for dysplasia as the baseline endoscopy during the screening period. Results from these surveillance biopsies must be negative for dysplasia (low-grade, high-grade, or indeterminant) prior to the first administration of study intervention * Females of childbearing potential must have a negative highly sensitive urine pregnancy test at screening and at Week I-0 prior to study intervention administration Exclusion Criteria: * Have UC limited to the rectum only or to less than (\<) 20 centimeter (cm) of the colon * Presence or history of coloni…