title: The cost and impact of scaling up pre-exposure prophylaxis for HIV prevention: a systematic review of cost-effectiveness modelling studies.
abstract: BACKGROUND
  Cost-effectiveness studies inform resource allocation, strategy, and policy development. However, due to their complexity, dependence on assumptions made, and inherent uncertainty, synthesising, and generalising the results can be difficult. We assess cost-effectiveness models evaluating expected health gains and costs of HIV pre-exposure prophylaxis (PrEP) interventions.
  
  
  RESULTS
  We conducted a systematic review comparing epidemiological and economic assumptions of cost-effectiveness studies using various modelling approaches. The following databases were searched (until January 2013): PubMed/Medline, ISI Web of Knowledge, Centre for Reviews and Dissemination databases, EconLIT, and region-specific databases. We included modelling studies reporting both cost and expected impact of a PrEP roll-out. We explored five issues: prioritisation strategies, adherence, behaviour change, toxicity, and resistance. Of 961 studies retrieved, 13 were included. Studies modelled populations (heterosexual couples, men who have sex with men, people who inject drugs) in generalised and concentrated epidemics from Southern Africa (including South Africa), Ukraine, USA, and Peru. PrEP was found to have the potential to be a cost-effective addition to HIV prevention programmes in specific settings. The extent of the impact of PrEP depended upon assumptions made concerning cost, epidemic context, programme coverage, prioritisation strategies, and individual-level adherence. Delivery of PrEP to key populations at highest risk of HIV exposure appears the most cost-effective strategy. Limitations of this review include the partial geographical coverage, our inability to perform a meta-analysis, and the paucity of information available exploring trade-offs between early treatment and PrEP.
  
  
  CONCLUSIONS
  Our review identifies the main considerations to address in assessing cost-effectiveness analyses of a PrEP intervention--cost, epidemic context, individual adherence level, PrEP programme coverage, and prioritisation strategy. Cost-effectiveness studies indicating where resources can be applied for greatest impact are essential to guide resource allocation decisions; however, the results of such analyses must be considered within the context of the underlying assumptions made. Please see later in the article for the Editors' Summary.
authors.affiliation: Department of Global Health, Academic Medical Centre, University of Amsterdam and Amsterdam Institute for Global Health and Development, The Netherlands. g.gomez@aighd.org
authors.forename: Gabriela B
authors.initials: GB
authors.lastname: Gomez
authors.forename: Annick
authors.initials: A
authors.lastname: Borquez
authors.forename: Kelsey K
authors.initials: KK
authors.lastname: Case
authors.forename: Ana
authors.initials: A
authors.lastname: Wheelock
authors.forename: Anna
authors.initials: A
authors.lastname: Vassall
authors.forename: Catherine
authors.initials: C
authors.lastname: Hankins
mesh_terms: D019380:Anti-HIV Agents / Q000191:economics* / Q000627:therapeutic use*; D003362:Cost-Benefit Analysis; D058872:Epidemics / Q000706:statistics & numerical data; D015658:HIV Infections / Q000191:economics* / Q000453:epidemiology / Q000517:prevention & control*; D020010:Heterosexuality / Q000706:statistics & numerical data; D006801:Humans; D008297:Male; D018803:Models, Economic; D010568:Peru / Q000453:epidemiology; D013019:South Africa / Q000453:epidemiology; D015819:Substance Abuse, Intravenous / Q000191:economics / Q000453:epidemiology; D014455:Ukraine / Q000453:epidemiology; D014481:United States / Q000453:epidemiology
chemical_list: D019380:Anti-HIV Agents
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