Cohort ANRS CO6 Primo

The ANRS CO6 PRIMO cohort is a French national cohort, established in 1996, dedicated to the follow-up of participants diagnosed at the stage of primary HIV infection.

With over 2,950 participants enrolled (as of 15 January 2026) recruited from nearly a hundred clinical sites across France at a steady rate of over a hundred new enrolments per year, it is likely the largest cohort of primary HIV infection in the world.

Its main objective is to study the pathophysiological, clinical, immunological, virological and behavioural aspects of HIV infection from its earliest stages. In particular, it aims to better understand the mechanisms of viral control, the formation of reservoirs, the kinetics of immunovirological markers, and the impact of early antiretroviral treatment on morbidity, mortality and long-term progression.

In 2010, the cohort incorporated the follow-up of seroconverting participants from the ANRS CO2 SEROCO cohort, the majority of whom were infected between 1988 and 1992, providing valuable historical perspective.

The cohort is distinguished by its rigorous methodology, which includes detailed questionnaires on modes of transmission and living conditions, genetic and immunological investigations, and the investigation of viral reservoirs — a major asset in the current context of research into HIV eradication.

It actively contributes to French and international treatment guidelines, to the European CASCADE/Eurocoord collaboration, and supports innovative clinical trials on early treatment.

Objectives

1. To explore the pathophysiological mechanisms of primary HIV-1 infection,
2. To assess the impact of early and prolonged treatment on the long-term prognosis of patients treated from the time of primary infection, particularly in terms of activation/inflammation and reduction of viral reservoirs, and in comparison with uninfected subjects,
3. To help document the epidemiology of HIV infection and the prevention of infection in the context of the spread of PrEP,
4. Contribute to national recommendations for therapeutic management and evaluate their implementation,
5. Use the observational data from the cohort to develop therapeutic trials in primary infection, continue long-term post-trial follow-up and prepare trials aimed at functional cure.