RecruitingPhase 2Drug trialEarly Vedolizumab as First-Line for Immune-Related Colitis Therapy TrialThe goal of this clinical trial is to compare the effectiveness and safety of Vedolizumab with a short course of steroids compared to standard course of steroids for the treatment of immune checkpoint inhibitor colitis (ICI colitis) in adults. The main questions it aims to answer are: * How many patients treated with Vedolizumab and a short course of steroids experience resolution of colitis at 8 weeks. * How many patients treated with a standard course of steroids experience resolution of colitis at 8 weeks. Participants will: Recieve 3 doses of Vedolizumab or a placebo (a look-alike substance that contains no drug) infusions over 6 weeks Receive intravenous Medrol daily for 3 days Receive Prednisone daily for 7 days Receive Prednisone or placebo taper daily Receive Sulfamethoxazole-Trimethoprim or placebo taper daily Weekly checkups and periodic tests