This is an open-label, Phase 3 clinical trial evaluating the efficacy of Tofacitinib based on remission in children with moderate to severe ulcerative colitis. The effects will be evaluated during an induction, maintenance, and extension period of taking the medication. Physical exams, blood and stool sample collection, and sporadic endoscopic evaluation are planned to take place throughout these periods.

This study aims to prospectively explore the real life short and longer term outcomes of Vedolizumab in pediatric inflammatory bowel disease and to develop a prediction model for treatment success based on Vedolizumab trough levels and other clinical and laboratory markers. Children under 18 years of age that have been diagnosed with IBD and their physician is starting treatment with Vedolizumab may be eligible.