Inclusion Criteria:  1. Has moderately to severely active IBD (UC or CD), initiating or ongoing IV induction treatment with vedolizumab in accordance with the current SmPC at baseline OR IBD participants receiving ongoing/maintenance IV vedolizumab treatment, with the option to switch to SC vedolizumab maintenance treatment.  Exclusion Criteria:  Prior history of intolerability, hypersensitivity, or other contraindications (active severe infections such as tuberculosis, sepsis, cytomegalovirus, listeriosis, and opportunistic infections such as Progressive Multifocal Leukoencephalopathy) to vedolizumab therapy as defined in the current SmPC. Current or planned participation in an interventional clinical trial for CD or UC. Cognitive incapacity, unwillingness or language barriers precluding adequate understanding or cooperation.