Durability of Virologic Response and/or Viral Resistance Patterns in Participants With Chronic Hepatitis C Who Have Been Previously Treated With Grazoprevir (MK-5172) (MK-5172-017)

Primary outcomes

1. Time to Viral Relapse

   Time frame: Up to ~60 months after enrollment in this study

   Viral relapse is defined as any participant who has confirmed HCV Ribonucleic acid (RNA) ≥ Lower limit of quantification (LLoQ) of 15 IU/mL and had achieved sustained virologic response (SVR) in the follow up in the prior treatment study. Time to relapse is defined as the time from last dose of study therapy taken in the prior treatment study until the date where HCV RNA is ≥LLoQ.

2. Persistence of Treatment-Emergent Nonstructural Protein (NS)3 and NS5A Resistance-associated Substitutions (RASs) in Participants With HCV Genotype (GT) 1a Infections

   Time frame: Up to ~60 months after enrollment in this study

   In adult participants with HCV RNA ≥1000 IU/mL at entry or during the study period, HCV sequence analysis was performed to evaluate the presence of RASs and the persistence of RASs over time.

3. Persistence of Treatment-Emergent NS3 and NS5A RASs in Participants With HCV Genotype 1b Infections

   Time frame: Up to ~60 months after enrollment in this study

   In adult participants with HCV RNA ≥1000 IU/mL at entry or during the study period, HCV sequence analysis was performed to evaluate the presence of RASs and the persistence of RASs over time.

4. Persistence of Treatment-Emergent NS3 and NS5A RASs in Participants With Genotype 4 Infections

   Time frame: Up to ~60 months after enrollment in this study

   In adult participants with HCV RNA ≥1000 IU/mL at entry or during the study period, HCV sequence analysis was performed to evaluate the presence of RASs and the persistence of RASs over time.

5. Number of Participants Who Experienced a Drug-Related Adverse Event (AE) During the Long-Term Follow-Up

   Time frame: Up to ~ 60 months after enrollment in this study

   An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. The study investigator determined whether the adverse event was drug-related.

6. Number of Participants Who Experienced a Drug-Related Serious Adverse Event (SAE) During the Long-Term Follow-Up

   Time frame: Up to ~60 months after enrollment in this study

   A serious adverse event (SAE) is any adverse experience occurring at any dose that either results in death, is life threatening, results in a persistent or significant disability/incapacity, results in or prolongs an existing inpatient hospitalization, is a congenital anomaly/birth defect, is a cancer, is an overdose (whether accidental or intentional), or other important medical events that may not result in death, not be life threatening, or not require hospitalization may be considered a serious adverse experience when, based upon appropriate medical judgment, the event may jeopardize the participant and may require medical or surgical intervention to prevent one of the outcomes listed previously. The study investigator determined whether the adverse event was drug-related.

7. Number of Participants Who Experienced an Event of Clinical Interest (ECI) During the Long-Term Follow-Up

   Time frame: Up to ~60 months after enrollment in this study

   An ECI includes spontaneous bacterial peritonitis, variceal bleeding, ascites, encephalopathy, hepatorenal syndrome, hepatocellular carcinoma, liver transplant, cardiovascular disease limited to angina and myocardial infarction, neurologic disorders limited to transient ischemic attack (TIA) or stroke, graft rejection in participants who have undergone liver or kidney transplant, or one of the following in participants from the MK-5172-052 (NCT02092350) base study: kidney transplant, decreased estimated glomerular filtration rate (eGFR), new onset diabetes, cryoglobulinemia, or post transplantation glomerulonephritis.