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The Ontario HIV Treatment Network Cohort Study (OCS) is a community-governed, province-wide research study aimed at improving the health and well-being of Ontarians living with HIV. Established in 1996, over 3,700 individuals actively participate at nine HIV clinics across the province. The OCS is the largest HIV cohort in Ontario and one of the largest in North America. It represents a diverse group of Ontarians living with HIV, including men and women of different ages, sexual orientations and ethnicities.

The OCS promotes clinical, psychosocial and socio-behavioural research to inform government policy, clinical practice and other care and support services. OCS team members work with leaders in the fields of HIV/AIDS, hepatitis C and other sexually transmitted and bloodborne infections.

A 2015 study assessing engagement in care among OCS participants between 2001 and 2011 found that 87% of participants were receiving regular viral load and CD4 tests; 77% were taking antiretroviral medication; and 76% had a suppressed viral load.


HIV Ontario Observational Database (HOOD) study funding committed


Ethics approval received, HOOD recruitment begins


HOOD & OHTN merge; HIV Information Infrastructure Project (HIIP) initiated


OHTN Cohort Study created; Governance Committee instituted


Agreement to link all HIV viral load testing data from Ontario Public Health Laboratories (PHL)


Interview added to study design, recruitment reinvigorated


Expansion of linkage with PHL: HIV genotyping (2009) and all additional tests (2010)


Data sharing agreement with Institute for Clinical Evaluative Studies (ICES)


Migration to online questionnaire; Redesign of Questionnaire