The goal of asthma treatment is to achieve and maintain asthma control and to reduce the future risk of exacerbations. Inhaled corticosteroids (ICS) are considered as the most effective anti- inflammatory treatment for all severities of persistent asthma. For children >=5 years of age and adolescents whose asthma is uncontrolled, low-dose ICS plus adjunctive therapy with long-acting beta agonist (LABA) is considered as effective. Thus, this study is designed to evaluate the efficacy and safety of FF (ICS component)/VI (LABA component) compared to FF alone for the treatment of asthma, in subjects aged 5 to 17 years old currently uncontrolled on ICS. The study will be conducted over a total duration of approximately 29 weeks: 4 week run-in period, 24-week double-blind treatment period and 1-week follow-up period. Subjects will be randomized to receive FDC of FF/VI or FF administered via ELLIPTA® dry powder inhaler (DPI). The dose of both FF/VI and FF alone will be selected based on the age of subjects. Subjects will receive a short acting beta 2 agonist (SABA) (albuterol /salbutamol) as a rescue medication throughout the study. A total of 870 subjects will be randomized in the study. Of this, 652 subjects will be aged 5 to 11 years (cohort A), and 218 will be aged 12 to 17 years inclusive (cohort B). ELLIPTA is a registered trademark of GlaxoSmithKline (GSK) group of companies.