A Study of Intravenous Vedolizumab Administered Every 4 Weeks in Japanese Participants With Moderate to Severe Ulcerative Colitis or Crohn's Disease

Inclusion Criteria: UC cohort 1. The participant has moderate to severe UC, who had previously shown clinical response in initial treatment with commercially available vedolizumab IV, then experienced secondary loss of response during maintenance therapy with commercially available vedolizumab IV Q8W. Previous "clinical response" is to be judged by the investigators referring to one of the following criteria. * Reduction of \>=2 points and \>=25% in modified Mayo score, and a decrease of \>=1 point in rectal bleeding subscore or rectal bleeding subscore of =\<1, from the start of initial treatment with commercially available vedolizumab IV. * Reduction of \>=2 points and \>=25% in partial Mayo score, and a decrease of \>=1 point in rectal bleeding subscore or rectal bleeding subscore of =\<1, from the start of initial treatment with commercially available vedolizumab IV. * Significant improvement on endoscopy (i.e., a decrease of \>=2 points in Mayo endoscopic subscore). "Secondary loss of response" is to be judged by the investigators referring to one of the following criteria. * Increase of \>=2 points in modified Mayo score, and an increase of \>=1 point in rectal bleeding subscore or rectal bleeding subscore \>=2, from the start of maintenance therapy with commercially available vedolizumab IV. * Increase of \>=2 points in partial Mayo score, and an increase of \>=1 point in rectal bleeding subscore or rectal bleeding subscore \>=2, from the start of maintenance therapy with commercially available vedolizumab IV. * Significant deterioration on endoscopy (i.e., an increase of \>=2 points in Mayo endoscopic subscore). 2. The participant has active UC as determined by a modified Mayo score of \>=5 at baseline (within 10 days prior to the start of treatment phase), with a Mayo rectal bleeding subscore of \>=1 at baseline (within 10 days prior to the start of treatment phase) and a Mayo endoscopic subscore of \>=1 as assessed by the central reader. CD cohort 1. The participant has moderate to severe CD, who had previously shown clinical response in initial treatment with commercially available vedolizumab IV, then experienced secondary loss of response during maintenance therapy with commercially available vedolizumab IV Q8W. Previous "clinical response" is to be judged by the investigators referring to one of the following criteria. * Reduction of \>=70 points in CDAI score from the start of initial treatment with commercially available vedolizumab IV. * Reduction of \>=3 points in HBI score from the start of initial treatment with commercially available vedolizumab IV. "Secondary loss of response" is to be judged by the investigators referring to one of the following criteria. * Increase of \>=70 points in CDAI score from the start of maintenance therapy with commercially available vedolizumab IV. * Increase of \>=3 points in HBI score from the start of maintenance therapy with commercially available vedolizumab IV. 2. The participant has active CD as determined by a CDAI score of \>=220 at baseline (within 10 days prior to the start of treatment phase). 3. The participant has a C-reactive protein (CRP) level \>3.0 mg/L during the screening phase. Exclusion Criteria: 1. The participant has had extensive colonic resection, subtotal or total colectomy. 2. The participant has received any of the investigational or approved non-biologic therapies (e.g., cyclosporine, tacrolimus or tofacitinib, except for those specifically listed as permitted medications) for the treatment of underlying disease within 30 days or 5 half-lives of screening (whichever is longer). 3. The participant has received any investigational or approved biologic or biosimilar agent other than vedolizumab within 60 days or 5 half-lives of screening (whichever is longer). 4. The participant has a clinically significant active infection (e.g., pneumonia, pyelonephritis or coronavirus disease 2019 \[COVID-19\]) within 30 days prior to screening or during screening, or has an ongoing chronic infection. 5. The participant has known or suspected intolerance or hypersensitivity to vedolizumab or closely related compounds, or any of the vedolizumab IV excipients. 6. The participant has active cerebral/meningeal disease, or signs/symptoms of progressive multifocal leukoencephalopathy (PML) or any history of PML at screening.