About The Study

Initiated in Montreal in 2002 and funded by CIHR in 2005, the Canadian Co-infection Cohort Study received support from the CTN starting in 2007. This national cohort study examines the effect of antiretroviral therapy (ART) on liver disease progression in people living with both HIV and hepatitis C virus (HCV). CTN 222 was the first observational cohort study approved by the CTN and included 950 participants from across 16 sites. With renewed funding from CIHR in 2009, and again in 2014, CTN 222 has expanded to include over 1600 people living with HCV and HIV.

If you would like more information on this clinical study, please refer to a participating site or visit the CTN 222 website at www.cocostudy.ca.


HCV is a virus that attacks the liver, causing liver disease (hepatitis). Because HCV can be contracted through the same routes as HIV (blood-to-blood contact, sexual contact, etc.) over 30% of people living with HIV worldwide also have HCV. Due to the success of antiretroviral therapies (ART), complications from comorbidities such as HCV have replaced AIDS-related infections as the primary health concern among people living with HIV.

End-stage liver disease (ESLD) due to HCV is one of the leading causes of illness and death in HIV/HCV+ people. The natural course of HCV is accelerated in people living with HIV. Initially, the ability of ART to restore the immune system was expected to improve liver health in this population. This was not the case, however, and liver disease continues to be a significant problem. In response, CTN 222 was formed to document and understand the social and biological factors that contribute to the interaction between these two viruses and their treatment and management.

Study Approach

CTN 222 is a long-term observational cohort study and includes a diverse group of people including men who have sex with men (MSM), current and ex-injection drug users, Indigenous people, and women. All eligible individuals who visit a participating clinic are invited to participate in the study. Those who initially decline the invitation are eligible to enrol in the future.

After giving informed consent and undergoing an initial evaluation, CTN 222 participants return approximately every 6 months, either as a part of clinical care or for study purposes alone. Clinical, sociodemographic, behavioural, medical, and treatment information is collected. Treatment and diagnosis history is also collected from past medical visits.


Since 2010, the CTN 222 team has published over 30 journal articles. This body of work is expansive, stretching across different areas of this complex area; this includes general cohort information, the effect of different treatment regimens, the impact of immunological factors, genetic variations, and lifestyle factors, and the interaction between participant sub-groups and liver-related health. One such characteristic is the effect of food insecurity on HIV-HCV outcomes which has spawned a CTN 222 sub-study, CTN 264.

Eligibility Requirements


  • HIV treatment naïve
  • Aged 16 years or older (or as provincial guidelines)
  • Documented HIV seropositive infection
  • Documented HCV infection or evidence of exposure
  • Able to provide informed consent

Additional Information

If you would like more information on this clinical study, please refer to a participating site or visit the CTN 222 website at www.cocostudy.ca.

Principal Investigators

Here’s who is leading this study.

Can’t find what you’re looking for? Email ctninfo@hivnet.ubc.ca.

Participating Sites

Here’s where this study is being conducted.