Zymfentra (Infliximab-dyyb) REal World Cohort STudy

This real-world observational study is following people with inflammatory bowel disease (Crohn's disease, ulcerative colitis, or related conditions) who are switching to or starting a new form of infliximab (a biologic medication) called Zymfentra, which is given as an injection under the skin rather than by IV infusion. **You may be eligible if...** - You are 18 or older - You have been diagnosed with Crohn's disease, ulcerative colitis, or inflammatory bowel disease unclassified - You are starting Zymfentra (subcutaneous infliximab-dyyb) at week 10 after IV induction therapy, OR you are switching from IV infliximab to Zymfentra during maintenance - You are expected to be followed at the participating clinic for at least 12 months **You may NOT be eligible if...** - You do not have a confirmed IBD diagnosis - You are unwilling to be followed up for the study period Talk to your doctor to see if this trial is right for you.