Inclusion Criteria:  Written informed consent form from the patient (≥18 years old) or from parent/legal guardian if patient is <18 years old. Written informed assent form from patient ≥11 years old. Age criteria: ≥6 years to ≤22 years of age. Diagnosis of Crohn's Disease Starting infliximab (or biosimilar) Anti-TNF naïve (never received infliximab, adalimumab, golimumab, certolizumab or anti-TNF biosimilar) Fecal calprotectin >250 µg/g or fecal lactoferrin >10 µg/g (up to 6 weeks prior to starting infliximab) or endoscopic evidence of active Crohn's disease (up to 90 days prior to starting infliximab) wPCDAI >12.5 (up to 6 weeks) prior to the first infliximab infusion Negative urine pregnancy test for ALL female subjects Negative TB (tuberculosis) blood test  Exclusion Criteria:  Diagnosis of ulcerative colitis or inflammatory bowel disease-unspecified Prior treatment with infliximab, adalimumab, certolizumab or golimumab (or anti-TNF biosimilar) Active or prior evidence in past 12 months of internal (abdominal/pelvic) penetrating fistula(e) Active intestinal stricture (luminal narrowing with pre-stenotic dilation >3mm), intra-abdominal abscess or perianal abscess Active Clostridium difficile infection or other known bacterial/viral gastroenteritis in last two weeks Current ileostomy, colostomy, ileoanal pouch, and/or previous extensive small bowel resection leading to short bowel syndrome History of autoimmune disease (including autoimmune hepatitis, primary sclerosing cholangitis, thyroiditis, psoriasis or juvenile idiopathic arthritis) Treatment with another investigational drug within four weeks. Treatment with intravenous antibiotics within four weeks. Planned continuation of 6-mercaptopurine or azathioprine (Imuran) during study. Planned continuation of methotrexate during study. Treatment with intravenous corticosteroids within two weeks. Currently pregnant, breast feeding or plans in next 12 months to become pregnant Inability or failure to provide informed assent/consent