The main purpose of this study is to see if taking benralizumab is effective in treating Severe Eosinophilic Asthma in patients 6 to 17 years old compared with placebo. Benralizumab is administered through a subcutaneous injection (shot). Participation in the study is divided into two parts. The first part will last up to 16 weeks or until an asthma attack or flare is experienced. The second part will last up to two years.

The purpose of this study is to see if taking mepolizumab is safe and effective in treating Hypereosinophilic syndrome (HES) in children and adolescent patients ages 6 to 17 years who are receiving standard of care (SoC) therapy. Mepolizumab is administered through a subcutaneous injection (shot). Participation in the study will last for about 64 weeks approximately (1 year and 3 months).