Trials Today

All Cohorts: - Male or female patients must be aged 6 to < 18 years of age at the time of signing the assent form and their caregiver signing the informed consent form. - Body weight greater than (>=) 15 kilograms (kg). EGPA Cohort: - Therapy with corticosteroids: The prescribed dose of oral corticosteroids (OCS) (greater than [>] 0.1 milligrams per kilogram per day (mg/kg/day), max dose of 50 milligrams per day (mg/day) must be stable (that is, no adjustment of the dose) for at least 4 weeks prior to baseline (Visit 2). - Immunosuppressive therapy: If receiving immunosuppressive therapy, the dosage must be stable for at least 4 weeks prior to baseline (Visit 2).

All Cohorts: - Any current malignancy or history of malignancy. - History of anaphylaxis to any biologic therapy or vaccine. - Known, pre-existing, clinically significant endocrine, autoimmune, metabolic, neurological, renal, gastrointestinal, hepatic, haematological, respiratory, or any other system abnormalities. - Previous receipt of benralizumab in an interventional clinical study. EGPA Cohort: - Diagnosed with granulomatosis with polyangiitis (previously known as Wegener'granulomatosis) or microscopic polyangiitis. - EGPA relapse: any deterioration in EGPA and/or organ-threatening EGPA that per Investigator judgement renders patients unstable in their EGPA within 3 months prior to screening (Visit 1) and through first administration of IP at baseline (Visit 2). - Life-threatening EGPA: imminently life-threatening EGPA disease within 3 months prior to screening (Visit 1) and through first administration of IP at baseline (Visit 2), as per Investigator judgement.