Biologics and Paediatric Enteral Nutrition in Crohn's Disease Study

Inclusion Criteria: * Eligible participants to the RCT are children or young adults (aged 6 to 18 years old) who have active CD (defined as a weighted paediatric Crohn's disease Activity Index score (wPCDAI) ≥ 12.5 or a Faecal Calprotectin level \>250 mg/kg and who have a clinical indication to initiate standard of care induction treatment with TNFα inhibitors (infliximab or adalimumab). * Eligible participants to the observational cohorts are children or young adults (aged 6 to 18 years old) who have active CD (defined as a weighted paediatric Crohn's disease Activity Index score (wPCDAI) ≥ 12.5 or a Faecal Calprotectin level \>250 mg/kg and who are due to initiate standard of care induction treatment with EEN therapy alongside TNFα inhibitors (infliximab or adalimumab) or standard of care induction treatment with EEN therapy without TNFα inhibitors (infliximab or adalimumab) Exclusion Criteria: * Inability to provide consent to participate in the study (i.e., this applies to young adults (aged 16-18 years) who are old enough but unable to provide consent and carers (of children aged 6-15 years old) who are unable to provide consent on behalf of their child). * Presence of stoma or of short bowel syndrome. * Patients currently receiving oral or intravenous steroids at a dosage \>20mg/day prednisolone or \>9mg/day budesonide. * Patients who start another induction therapy (e.g., high dosage of steroids) or change the dose of background immunomodulator (azathioprine, mercaptopurine, methotrexate) within the past 4 weeks. * CD with a major fistulising or symptomatic fibrotic stricturing phenotype. * Patients with comorbid anorexia nervosa. * Any clinical contraindication to use of exclusive enteral nutrition or partial enteral nutrition. * Patients tested positive for blood-borne viruses such as HIV and Hepatitis B and C. * Patients with untreated tuberculosis (latent or active). * Current enrolment in other studies of an investigational product or dietary intervention. * Food allergies, which do not permit participation in the study (e.g., cow's milk allergy). * Pregnant and/or breastfeeding individuals.