title: Investigating combination HIV prevention: isolated interventions or complex system.
abstract: BACKGROUND
  Treatment as prevention has mobilized new opportunities in preventing HIV transmission and has led to bold new UNAIDS targets in testing, treatment coverage and transmission reduction. These will require not only an increase in investment but also a deeper understanding of the dynamics of combining behavioural, biomedical and structural HIV prevention interventions. High-income countries are making substantial investments in combination HIV prevention, but is this investment leading to a deeper understanding of how to combine interventions? The combining of interventions involves complexity, with many strategies interacting with non-linear and multiplying rather than additive effects.
  
  
  CONCLUSIONS
  Drawing on a recent scoping study of the published research evidence in HIV prevention in high-income countries, this paper argues that there is a gap between the evidence currently available and the evidence needed to guide the achieving of these bold targets. The emphasis of HIV prevention intervention research continues to look at one intervention at a time in isolation from its interactions with other interventions, the community and the socio-political context of their implementation. To understand and evaluate the role of a combination of interventions, we need to understand not only what works, but in what circumstances, what role the parts need to play in their relationship with each other, when the combination needs to adapt and identify emergent effects of any resulting synergies. There is little development of evidence-based indicators on how interventions in combination should achieve that strategic advantage and synergy. This commentary discusses the implications of this ongoing situation for future research and the required investment in partnership. We suggest that systems science approaches, which are being increasingly applied in other areas of public health, could provide an expanded vocabulary and analytic tools for understanding these complex interactions, relationships and emergent effects.
  
  
  CONCLUSIONS
  Relying on the current linear but disconnected approaches to intervention research and evidence we will miss the potential to achieve and understand system-level synergies. Given the challenges in sustaining public health and HIV prevention investment, meeting the bold UNAIDS targets that have been set is likely to be dependent on achieving systems level synergies.
authors.affiliation: Australian Research Centre in Sex, Health and Society, La Trobe University, Melbourne, Australia.|Centre for Social Research in Health, University of New South Wales, Sydney, Australia; Graham.brown@latrobe.edu.au.
authors.forename: Graham
authors.initials: G
authors.lastname: Brown
authors.affiliation: Australian Research Centre in Sex, Health and Society, La Trobe University, Melbourne, Australia.
authors.forename: Daniel
authors.initials: D
authors.lastname: Reeders
authors.affiliation: Australian Research Centre in Sex, Health and Society, La Trobe University, Melbourne, Australia.|Centre for Social Research in Health, University of New South Wales, Sydney, Australia.
authors.forename: Gary W
authors.initials: GW
authors.lastname: Dowsett
authors.affiliation: Australian Research Centre in Sex, Health and Society, La Trobe University, Melbourne, Australia.|Kirby Institute, University of New South Wales, Sydney, Australia.
authors.forename: Jeanne
authors.initials: J
authors.lastname: Ellard
authors.affiliation: Australian Research Centre in Sex, Health and Society, La Trobe University, Melbourne, Australia.
authors.forename: Marina
authors.initials: M
authors.lastname: Carman
authors.affiliation: Australian Research Centre in Sex, Health and Society, La Trobe University, Melbourne, Australia.
authors.forename: Natalie
authors.initials: N
authors.lastname: Hendry
authors.affiliation: Australian Research Centre in Sex, Health and Society, La Trobe University, Melbourne, Australia.
authors.forename: Jack
authors.initials: J
authors.lastname: Wallace
mesh_terms: D019380:Anti-HIV Agents / Q000008:administration & dosage*; D004359:Drug Therapy, Combination; D015658:HIV Infections / Q000517:prevention & control*; D006801:Humans; D011634:Public Health
chemical_list: D019380:Anti-HIV Agents
keywords: combination HIV prevention; complex systems; evaluation; evidence; intervention research; treatment as prevention