title: Assessing the effect of HIV counselling and testing on HIV acquisition among South African youth.
abstract: OBJECTIVE
  Youth aged 15-24 years in sub-Saharan Africa are at a high risk for HIV acquisition and urgently need HIV prevention interventions. HIV counselling and testing (HCT) is designed to promote HIV prevention. However the impact of HCT on HIV acquisition has never been assessed among youth. We assess the impact of HCT on HIV acquisition among South African youth.
  
  
  METHODS
  Data came from an annual HIV survey for persons aged 15 years and over, nested within a socio-demographic household surveillance in a geographically defined area of KwaZulu-Natal. Within this population, we used data from 2006 to 2011 to construct a cohort of HIV-uninfected youth aged 15-24 years.
  
  
  METHODS
  We compared youth who reported knowing their HIV status from HCT with those who reported not knowing their HIV status for time to HIV seroconversion using time-varying marginal structural Cox proportional hazards models.
  
  
  RESULTS
  The cohort included 3959 HIV-uninfected youth, of whom 1167 (29%) reported HCT at baseline and an additional 1064 (27%) reported HCT during follow up. Youth experienced 248 seroconversions over 8536 person-years, an incidence rate of 2.91 per 100 person-years [95% confidence interval (CI) 2.56-3.28]. In crude analysis, HCT was not associated with HIV incidence (hazard ratio 1.02, 95% CI 0.79-1.31], but in marginal structural models weighted for risk factors, HCT was protective (hazard ratio 0.59, 95% CI 0.45-0.78).
  
  
  CONCLUSIONS
  In this high-risk population, after accounting for differences in underlying HIV acquisition risk, HCT was associated with lower HIV incidence. HCT scale-up may have prevention benefits for HIV-uninfected youth.
authors.affiliation: aDepartment of Epidemiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA bAfrica Centre for Health and Population Studies, University of KwaZulu-Natal, Mtubatuba, South Africa cDepartment of Obstetrics and Gynecology dGlobal Health Institute, Duke University, Durham, North Carolina eDepartment of Global Health and Population, Harvard School of Public Health, Boston, Massachusetts fDepartment of Medicine, School of Medicine gDepartment of Health Behavior and Health Education, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA hAcademic Unit of Human Development and Health, University of Southampton, Southampton, UK.
authors.forename: Nora E
authors.initials: NE
authors.lastname: Rosenberg
authors.forename: Daniel
authors.initials: D
authors.lastname: Westreich
authors.forename: Till
authors.initials: T
authors.lastname: Bärnighausen
authors.forename: William C
authors.initials: WC
authors.lastname: Miller
authors.forename: Frieda
authors.initials: F
authors.lastname: Behets
authors.forename: Suzanne
authors.initials: S
authors.lastname: Maman
authors.forename: Marie-Louise
authors.initials: ML
authors.lastname: Newell
authors.forename: Audrey
authors.initials: A
authors.lastname: Pettifor
mesh_terms: D000293:Adolescent; D015331:Cohort Studies; D003376:Counseling; D003955:Diagnostic Tests, Routine / Q000706:statistics & numerical data*; D005260:Female; D015658:HIV Infections / Q000175:diagnosis* / Q000453:epidemiology / Q000517:prevention & control*; D006801:Humans; D015994:Incidence; D008297:Male; D013019:South Africa / Q000453:epidemiology; D055815:Young Adult