A Study to Investigate the Efficacy and Safety of Tezepelumab Compared With Placebo in Children 5 to < 12 Years Old With Severe Asthma

This is a phase-3 multicentre, double-blind, parallel-group placebo-controlled, randomised study. The study will comprise of: 1. Screening/Run-in period of 4 to 6 weeks, 2. 52-week double-blind Treatment period, 3. Post-treatment Follow-up period of 12 weeks. Participants will be randomised 2:1 to receive either tezepelumab or placebo administered by (SC) Subcutaneous injections for 52 weeks (double-blind Treatment period). There will then be a 12-week off-treatment Follow-up period for participants who do not continue in the optional open-label Active Treatment Extension period. An optional open-label Active Treatment Extension will allow all eligible participants the opportunity to receive active treatment with tezepelumab. The Active Treatment Extension period of the study will start following the 52-week double-blind Treatment period and will consist of a 104-week open-label Treatment period prior to the 12-week post-treatment Follow-up period.