MOdel-Informed Precision Dosing of Ustekinumab and VEdolizumab in Inflammatory Bowel Disease

The goal of this clinical trial is to investigate if dosage of Ustekinumab (UST) and Vedolizumab (VDZ) based on Model-Informed Precision Dosing (MIPD) is equally as efficient in keeping adults with Inflammatory Bowel Disease (IBD) in remission as management based on what the treating physician deems best. The main question is: Is using pharmacokinetic-pharmacodynamic (PK-PD) models to predict the appropriate dose and dosing interval for VDZ and UST at least as effective as current practices in maintaining IBD remission. As above mentioned the comparison-group is adults with IBD, treated with UST or VDZ, managed as the physician deems best. Participants will: Have blood and stool tests done, as well as answer a questionnaire 4th weekly Have their dosage frequency decided on either by the PK-model or as the physician deems best visit the clinic once every 24 weeks for checkups. Have an endoscopy done at completion of the study (if the disease is primarily located in the small intestine, MRI or capsule endoscopy will be used instead)