title: Designing an optimal HIV programme for South Africa: Does the optimal package change when diminishing returns are considered?
abstract: South Africa has a large domestically funded HIV programme with highly saturated coverage levels for most prevention and treatment interventions. To further optimise its allocative efficiency, we designed a novel optimisation method and examined whether the optimal package of interventions changes when interaction and non-linear scale-up effects are incorporated into cost-effectiveness analysis.
  
  
  
  The conventional league table method in cost-effectiveness analysis relies on the assumption of independence between interventions. We added methodology that allowed the simultaneous consideration of a large number of HIV interventions and their potentially diminishing marginal returns to scale. We analysed the incremental cost effectiveness ratio (ICER) of 16 HIV interventions based on a well-calibrated epidemiological model that accounted for interaction and non-linear scale-up effects, a custom cost model, and an optimisation routine that iteratively added the most cost-effective intervention onto a rolling baseline before evaluating all remaining options. We compared our results with those based on a league table.
  
  
  
  The rank order of interventions did not differ substantially between the two methods- in each, increasing condom availability and male medical circumcision were found to be most cost-effective, followed by anti-retroviral therapy at current guidelines. However, interventions were less cost-effective throughout when evaluated under the optimisation method, indicating substantial diminishing marginal returns, with ICERs being on average 437% higher under our optimisation routine.
  
  
  
  Conventional league tables may exaggerate the cost-effectiveness of interventions when programmes are implemented at scale. Accounting for interaction and non-linear scale-up effects provides more realistic estimates in highly saturated real-world settings.
authors.affiliation: Health Economics and Epidemiology Research Office (HE2RO), Department of Internal Medicine, School of Clinical Medicine, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: Calvin
authors.initials: C
authors.lastname: Chiu
authors.affiliation: Centre for Infectious Disease Epidemiology and Research (CIDER), University of Cape Town, Cape Town, South Africa.
authors.forename: Leigh F
authors.initials: LF
authors.lastname: Johnson
authors.affiliation: Health Economics and Epidemiology Research Office (HE2RO), Department of Internal Medicine, School of Clinical Medicine, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa. ljamieson@heroza.org.
authors.forename: Lise
authors.initials: L
authors.lastname: Jamieson
authors.affiliation: Center for Global Health and Development, Department of International Health, Boston University, Boston, USA.
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Larson
authors.affiliation: Health Economics and Epidemiology Research Office (HE2RO), Department of Internal Medicine, School of Clinical Medicine, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.|Center for Global Health and Development, Department of International Health, Boston University, Boston, USA.
authors.forename: Gesine
authors.initials: G
authors.lastname: Meyer-Rath
mesh_terms: D002944:Circumcision, Male / Q000191:economics; D003362:Cost-Benefit Analysis; D005260:Female; D015658:HIV Infections / Q000191:economics* / Q000517:prevention & control*; D006679:HIV Seropositivity / Q000191:economics; D006293:Health Promotion / Q000191:economics*; D006801:Humans; D008297:Male; D016730:Program Development / Q000191:economics*; D013019:South Africa
keywords: Cost-effectiveness analysis; HIV; Health economics; Modelling; Optimisation; South Africa