Crohn's Disease (CD) is an inflammatory bowel disease. It can lead to significant complications and discomfort in the stomach and intestines. Crohn's disease is a debilitating, incurable disease of immune cells; it affects almost 1 million people in the United States. CD is characterized by inflammation of the stomach and intestine as well as organs outside of the intestines such as the skin, eyes, and joints. Current therapies to treat CD aim to suppress the patient's immune cells but these therapies become ineffective for the majority of patients and lead to complications including the requirement for surgical bowel resection, impaired quality of life, and lifelong disability. Hematopoietic stem cell transplantation (HCT) is a procedure used to treat a number of medical conditions including Crohn's disease. To improve success of HCT in CD doctors considered combining transplant with other drugs to improve the chances of achieving remission and also maintaining the remission. The Investigators' plan in this study is to incorporate the drug Vedolizumab after transplant to test if this drug will improve remission and make patients healthier.