Vedolizumab IV in Pediatric Participants With Ulcerative Colitis (UC) or Crohn's Disease (CD)

Inclusion Criteria

• Participants weighs >=10 kg at the time of randomization.
• Has a medical history of moderately to severely active UC during Screening defined as complete Mayo score of 6 to 12, and a total Mayo subscores of stool frequency and rectal bleeding >=4 and Mayo endoscopy subscore >=2, or has moderately to severely active CD defined as simple endoscopic score for Crohn's disease (SES-CD) >=7, and the CDAI components of average daily abdominal pain score of greater than (>) 1 for the 7 days prior, and total number of liquid/very soft stools >10 within 7 days prior to first dose of study drug.
• Has evidence of UC extending proximal to the rectum (that is, not limited to proctitis) or evidence of CD involving the ileum and/or colon, at a minimum.
• Has extensive colitis or pancolitis of >8 years duration or left-sided colitis of >12 years duration must have documented evidence that a surveillance colonoscopy was performed within 12 months prior to their first dose of study drug.
• Has a family history of colorectal cancer (that is, first-degree relative), personal history of increased colorectal cancer risk, or other known risk factor must be up-to-date on colorectal cancer surveillance.
• The participant's vaccinations are up to date.
• Has demonstrated an inadequate response to, loss of response to, or intolerance of at least 1 of the following agents as defined below:

Corticosteroids:

• Signs and/or symptoms of persistently active disease despite a history of at least one 4-week induction regimen that included a dose equivalent to or more than prednisone 1 milligram per kilogram (mg/kg) daily orally for 2 weeks or IV for 1 week.

OR

• Two failed attempts to taper corticosteroids to below a dose equivalent to prednisone 10 mg daily orally on 2 separate occasions.

OR

• History of significant intolerance to corticosteroids (including, but not limited to, Cushing's syndrome, osteopenia/osteoporosis, hyperglycemia, insomnia, and infection).

Immunomodulators:

• Signs and symptoms of persistently active disease despite a history of at least one 8-week regimen of oral azathioprine (AZA) (>=1.5 milligram per kilogram per day [mg/kg/day]) or 6-mercaptopurine (6-MP) mg/kg (>=1.0 mg/kg/day) or methotrexate (MTX) (>=10 milligram per square meter [mg/m^2] once a week).

OR

• History of intolerance of at least 1 immunomodulator (including, but not limited to, nausea/vomiting, abdominal pain, pancreatitis, liver function test (LFT) abnormalities, lymphopenia, thiopurine methyltransferase genetic mutation, infection).

Tumor necrosis factor-alpha (TNF-α) antagonists:

• Signs and symptoms of persistently active disease despite a history of at least 1 induction regimen of infliximab 5 mg/kg IV at Week 0 and Weeks 2 and 6 or adalimumab 2-week regimen of 160 mg on Day 1 and 80 mg on Day 15 if >=40 kg or 80 mg on Day 1 and 40 mg on Day 15 if =5 millimeter (mm). Participants with documented previously treated TB with a negative QuantiFERON test can be included in the study.
• Clinically significant current or recent history (within 1 year prior to enrollment) of alcohol dependence or illicit drug use.
• Has a current diagnosis of indeterminate colitis (Inflammatory bowel disease unclassified [IBDU]). For participants less than 6 years of age, any findings that suggest monogenic very early onset inflammatory bowel disease should be excluded.
• Has evidence of abdominal abscess or toxic megacolon at the initial Screening Visit.
• Has ileostomy, colostomy, ileo-anal pouch, or known fixed symptomatic stenosis of the intestine.
• Has extensive colonic resection, example, subtotal or total colectomy.
• Has a history or evidence of adenomatous colonic polyps that have not been removed.
• Has a history or evidence of colonic mucosal dysplasia.
• Has chronic hepatitis B virus (HBV) infection* or chronic hepatitis C virus (HCV) infection. * HBV immune participants (that is, being hepatitis B surface antigen [HBs