An Efficacy and Safety Study of Vedolizumab Intravenous (IV) Compared to Adalimumab Subcutaneous (SC) in Participants With Ulcerative Colitis

The drug being tested in this study is called vedolizumab. Vedolizumab is being tested to treat people who have ulcerative colitis. This study will look at the stool frequency, rectal bleeding and findings on endoscopy of people who take vedolizumab compared to those who take adalimumab. The study will enroll approximately 658 participants. Participants will be randomly assigned (by chance, like flipping a coin) to one of the two treatment groups-which will remain undisclosed to the patient and study doctor during the study (unless there is an urgent medical need): * Vedolizumab 300 mg IV * Adalimumab 160 mg on Day 1 followed by 80 mg on Week 2 then 40 mg every 2 weeks SC All participants will receive 1 intravenous infusion on Day 1 and Weeks 2, 6, 14, 22, 30, 38, and 46. All participants will also receive 4 SC injections on Day 1 or 2 SC injections each on Days 1 and 2, followed by 2 SC injections in 1 day on Week 2 and then 1 SC injection every 2 weeks for up to Week 50. All participants will be asked to record the symptoms of ulcerative colitis in a daily diary. This multi-center trial will be conducted worldwide. The overall time to participate in this study is 79 weeks. Participants will make approximately 11 visits to the clinic, and will be contacted by telephone 6 months after last dose of study drug for a follow-up assessment.