 After completion of 48 weeks, all participants will be given the option to participate in an extension phase of the study. Gilead will provide FTAF until a The participant turns 18 years old and FTAF is commercially available for use in adults in the country in which the participant is enrolled or b, FTAF becomes commercially available for pediatric use in the country in which the participant is enrolled or c, Gilead Sciences elects to terminate development of FTAF in the applicable country. 