An Open-Label, Phase 3 Study to Evaluate the Pharmacokinetics, Safety, and Immunogenicity of Vedolizumab Subcutaneous in Pediatric Subjects With Moderately to Severely Active Ulcerative Colitis or Crohn's Disease Who Achieved Clinical Response Following Open-Label Vedolizumab Intravenous Therapy

The drug being tested in this study is vedolizumab. Vedolizumab is being tested to treat pediatric participants with moderate to severe active UC or CD who achieved clinical response following open-label vedolizumab intravenous (IV) therapy. The study will look at the pharmacokinetics, safety, and immunogenicity of vedolizumab. The study will enroll approximately 70 patients. During the Induction Period participants will receive 3 doses of vedolizumab IV infusion at Day 1, Week 2, and Week 6 based on their weight at Baseline as: * Participants ≥30 kilograms (kg), Vedolizumab (High Dose) * Pa…