Inclusion Criteria for Treatment Cohort 1. Has completed Week 34 of Study VedolizumabSC-3003 (NCT06100289) and achieved clinical response at Week 34 and was corticosteroid-free for at least the last 4 weeks (Week 30 to Week 34). Clinical response for participants with UC is defined as a reduction of partial Mayo score of >=2 points and >= 25 percentage (%) from baseline (from VedolizumabSC-3003 [NCT06100289]), including a >=1-point decrease in the Mayo stool frequency subscore and a >=1-point reduction in the rectal bleeding subscore or absolute rectal bleeding subscore of less than or equal to (<=) 1 point. Clinical response for participants with CD is defined as a pediatric Crohn's disease activity index (PCDAI) <=30 with a reduction in the PCDAI of >=15 points from baseline (from VedolizumabSC-3003 [NCT06100289]).

Inclusion Criteria for Observational Cohort

1. Has received at least 1 dose of vedolizumab during Study VedolizumabSC-3003 (NCT06100289) and early terminated OR completed the Week 34 clinic visit of Study VedolizumabSC-3003 (NCT06100289) but was not eligible to enroll in the treatment cohort of this study.

Exclusion Criteria for Treatment Cohort

1. Has hypersensitivity or allergies to vedolizumab or any of its excipients.
2. The participant currently requires major surgical intervention for UC or CD (example, bowel resection), or is anticipated to require major surgical intervention for UC or CD during the study.