The rates of sustained virologic response were @ % ( @ % confidence interval -LSB- CI -RSB- , @ to @ ) in the group that received @ weeks of ledipasvir-sofosbuvir ; @ % ( @ % CI , @ to @ ) in the group that received @ weeks of ledipasvir-sofosbuvir plus ribavirin ; @ % ( @ % CI , @ to @ ) in the group that received @ weeks of ledipasvir-sofosbuvir ; and @ % ( @ % CI , @ to @ ) in the group that received @ weeks of ledipasvir-sofosbuvir plus ribavirin .