Treatment as prevention enrolling at least 75% of individuals on ART will be needed to significantly reduce HIV prevalence in a HIV cohort

Background: "Treatment as Prevention" (TasP) aims to reduce new HIV infections through higher enrolment on suppressive antiretroviral therapy (ART). Objectives: We studied the current epidemic and possible impact of TasP in a French HIV cohort including MSM and migrant subjects. Study design: Socio-demographic, clinical and laboratory variables were collected during the follow-up of 6995 HIV-infected patients. The numbers of individuals living with HIV in each year were estimated from diagnoses up to that year minus recorded deaths. Patients were classified according to gender, transmission mode, country of birth and treatment status. Results: The cohort includes 6995 individuals diagnosed from 1985 to 2015, of whom 72% were men. Unprotected sexual intercourse was the main mode of transmission. Women were more likely to be migrants (45% versus 13%), whereas men were more likely to have been born in France (52% versus 27%). Diagnoses were more correlated with untreated than treated prevalence in each group. MSM diagnoses was strongly correlated to untreated prevalence whatever the country of birth (p < 0.0001). However, heterosexual diagnoses were better correlated with prevalence within individual country groups (b = 0.29 female diagnoses/year per untreated male born in France, compared to b = 0.73 for foreigners). Using these transmission rates, mathematical modelling estimated that enrolling 75% of untreated individuals per year would decrease diagnoses tenfold by 2021. Conclusions: Enrolling at least 75% of individuals on ART is necessary to substantially impact numbers of new HIV infections in this cohort. Treatment as prevention will actually be effective to reduce HIV prevalence.