title: PrEP for key populations in combination HIV prevention in Nairobi: a mathematical modelling study.
abstract: The HIV epidemic in the population of Nairobi as a whole is in decline, but a concentrated sub-epidemic persists in key populations. We aimed to identify an optimal portfolio of interventions to reduce HIV incidence for a given budget and to identify the circumstances in which pre-exposure prophylaxis (PrEP) could be used in Nairobi, Kenya.
  
  
  
  A mathematical model was developed to represent HIV transmission in specific key populations (female sex workers, male sex workers, and men who have sex with men [MSM]) and among the wider population of Nairobi. The scale-up of existing interventions (condom promotion, antiretroviral therapy, and male circumcision) for key populations and the wider population as have occurred in Nairobi is represented. The model includes a detailed representation of a PrEP intervention and is calibrated to prevalence and incidence estimates specific to key populations and the wider population.
  
  
  
  In the context of a declining epidemic overall but with a large sub-epidemic in MSM and male sex workers, an optimal prevention portfolio for Nairobi should focus on condom promotion for male sex workers and MSM in particular, followed by improved antiretroviral therapy retention, earlier antiretroviral therapy, and male circumcision as the budget allows. PrEP for male sex workers could enter an optimal portfolio at similar levels of spending to when earlier antiretroviral therapy is included; however, PrEP for MSM and female sex workers would be included only at much higher budgets. If PrEP for male sex workers cost as much as US$500, average annual spending on the interventions modelled would need to be less than $3·27 million for PrEP for male sex workers to be excluded from an optimal portfolio. Estimated costs per infection averted when providing PrEP to all female sex workers regardless of their risk of infection, and to high-risk female sex workers only, are $65 160 (95% credible interval [CrI] $43 520-$90 250) and $10 920 (95% CrI $4700-$51 560), respectively.
  
  
  
  PrEP could be a useful contribution to combination prevention, especially for under-served key populations in Nairobi. An ongoing demonstration project will provide important information regarding practical aspects of implementing PrEP for key populations in this setting.
  
  
  
  The Bill & Melinda Gates Foundation.
authors.affiliation: Department of Infectious Disease Epidemiology, Imperial College London, London, UK. Electronic address: ide.cremin05@imperial.ac.uk.
authors.forename: Ide
authors.initials: I
authors.lastname: Cremin
authors.affiliation: Department of Medical Microbiology, University of Manitoba, Winnipeg, Canada; Department of Medical Microbiology, University of Nairobi, Nairobi, Kenya; Centre for the AIDS Programme of Research in South Africa (CAPRISA), Durban, South Africa.
authors.forename: Lyle
authors.initials: L
authors.lastname: McKinnon
authors.affiliation: Department of Medical Microbiology, University of Manitoba, Winnipeg, Canada; Department of Medical Microbiology, University of Nairobi, Nairobi, Kenya; Sex Worker Outreach Program, Nairobi, Kenya.
authors.forename: Joshua
authors.initials: J
authors.lastname: Kimani
authors.affiliation: Ministry of Health, Nairobi, Kenya.
authors.forename: Peter
authors.initials: P
authors.lastname: Cherutich
authors.affiliation: Department of Medical Microbiology, University of Manitoba, Winnipeg, Canada; Department of Medical Microbiology, University of Nairobi, Nairobi, Kenya; Sex Worker Outreach Program, Nairobi, Kenya.
authors.forename: Gloria
authors.initials: G
authors.lastname: Gakii
authors.affiliation: Department of Medical Microbiology, University of Nairobi, Nairobi, Kenya; Sex Worker Outreach Program, Nairobi, Kenya.
authors.forename: Festus
authors.initials: F
authors.lastname: Muriuki
authors.affiliation: Avenir Health, Washington, DC, USA.
authors.forename: Katharine
authors.initials: K
authors.lastname: Kripke
authors.affiliation: Pharos Global Health Advisors, Washington, DC, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Hecht
authors.affiliation: LVCT Health, Nairobi, Kenya.
authors.forename: Michael
authors.initials: M
authors.lastname: Kiragu
authors.affiliation: Department of Infectious Disease Epidemiology, Imperial College London, London, UK.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Smith
authors.affiliation: Department of Infectious Disease Epidemiology, Imperial College London, London, UK.
authors.forename: Wes
authors.initials: W
authors.lastname: Hinsley
authors.affiliation: Department of Medical Microbiology, University of Manitoba, Winnipeg, Canada; Department of Medical Microbiology, University of Nairobi, Nairobi, Kenya; Sex Worker Outreach Program, Nairobi, Kenya.
authors.forename: Lawrence
authors.initials: L
authors.lastname: Gelmon
authors.affiliation: Department of Infectious Disease Epidemiology, Imperial College London, London, UK.
authors.forename: Timothy B
authors.initials: TB
authors.lastname: Hallett
mesh_terms: D000328:Adult; D019380:Anti-HIV Agents / Q000008:administration & dosage* / Q000191:economics; D058872:Epidemics; D005260:Female; D015658:HIV Infections / Q000191:economics / Q000517:prevention & control* / Q000635:transmission / Q000821:virology; D018451:Homosexuality, Male / Q000706:statistics & numerical data; D006801:Humans; D007630:Kenya; D008297:Male; D008962:Models, Theoretical; D065129:Pre-Exposure Prophylaxis / Q000191:economics; D060386:Sex Workers / Q000706:statistics & numerical data; D055815:Young Adult
chemical_list: D019380:Anti-HIV Agents