The rates of sustained virologic response were high in all treatment groups : 94 % ( 95 % confidence interval [ CI ] , 87 to 97 ) in the group that received 12 weeks of ledipasvir-sofosbuvir ; 96 % ( 95 % CI , 91 to 99 ) in the group that received 12 weeks of ledipasvir-sofosbuvir and ribavirin ; 99 % ( 95 % CI , 95 to 100 ) in the group that received 24 weeks of ledipasvir-sofosbuvir ; and 99 % ( 95 % CI , 95 to 100 ) in the group that received 24 weeks of ledipasvir-sofosbuvir and ribavirin .