- Background Direct acting antivirals for hepatitis C virus have shown dramatic results in clinical trials. However, their effectiveness has yet to be demonstrated within observational cohorts which lack exclusion criteria found in randomized control trials. Aim To determine the effectiveness of dasabuvir/ombitasvir/paritaprevir/ritonavir in achieving sustained virological response. Methods Retrospective observational cohort study of all Clalit Health Services members with hepatitis C virus genotype 1 who were dispensed dasabuvir/ombitasvir/paritaprevir/ritonavir from January 1, 2015 to-November 31, 2015. Results There were 564 participants during the study period. The average age was 61.9 years, 52.0% were male, and 61.5% were born Eastern/Central Europe or Central Asia. The prevalence of diabetes was 31.7% and 70.3% were overweight/obese. Cirrhosis was present in 41.0% of participants, of whom 52.8% had stage 4 fibrosis. Of the cohort, 416 (74.8%) had follow-up viral load testing at 10 or more weeks after the end of treatment. We report a sustained virological response of 98.8% among those tested. Conclusions Treatment with dasabuvir/ombitasvir/paritaprevir/ritonavir demonstrated a near universal effectiveness in achieving a sustained virological response among HCV patients in a large cohort.