We neglect primary HIV prevention at our peril
Authors: Michael T Isbell, Nduku Kilonzo, Owen Mugurungi, Linda-Gail Bekker
Journal: The Lancet HIV (2016)

Inspired by a steady decline in new HIV infections and AIDS-related deaths, the sustainable development goals call for ending the AIDS epidemic as a public health threat by 2030. However, the world is not on track to end the epidemic. In particular, the pace at which new HIV infections are declining is substantially slower than the fall in AIDS-related deaths, and epidemic control remains out of reach. In 2015, the estimated number of new HIV infections in adults (1·9 million worldwide) was no fewer than in 2010.1UNAIDSGlobal AIDS Update. UNAIDS, Geneva2016http://www.unaids.org/sites/default/files/media_asset/global-AIDS-update-2016_en.pdfGoogle Scholar Unless the decline in new HIV infections is accelerated, a rebound of the epidemic is likely, with potentially catastrophic consequences for the communities most vulnerable to HIV. Although antiretroviral therapy (ART) is powerfully effective in reducing the risk of HIV transmission,2Cohen MS Chen YQ McCauley M et al.Prevention of HIV-1 infections with early antiretroviral therapy.N Engl J Med. 2011; 365: 493-505Crossref PubMed Scopus (5412) Google Scholar HIV transmission will persist even with achievement of the ambitious UNAIDS 90-90-90 target for ART.2Cohen MS Chen YQ McCauley M et al.Prevention of HIV-1 infections with early antiretroviral therapy.N Engl J Med. 2011; 365: 493-505Crossref PubMed Scopus (5412) Google Scholar Only by combining scaled up ART with substantially more effective prevention of HIV acquisition will the decline in the global HIV burden accelerate. The urgency of strengthening HIV prevention is emphasised by demographic realities, as the proportion of the population younger than age 15 exceeds 40% in all but eight countries in sub-Saharan Africa.3UNAIDSFast-track: ending the AIDS epidemic by 2030. United Nations Programme on HIV/AIDS, Geneva2014http://www.unaids.org/sites/default/files/media_asset/JC2686_WAD2014report_en.pdfGoogle Scholar In the coming years, as this especially large cohort of young people enters young adolescence and young adulthood, when HIV acquisition risks are greatest, failing to strengthen primary HIV prevention will undermine the benefits of treatment.3UNAIDSFast-track: ending the AIDS epidemic by 2030. United Nations Programme on HIV/AIDS, Geneva2014http://www.unaids.org/sites/default/files/media_asset/JC2686_WAD2014report_en.pdfGoogle Scholar In the high-burden countries of eastern and southern Africa, this demographic bulge poses particular risks of HIV acquisition for adolescent girls and young women. Efforts to prevent new HIV infections early in the epidemic were stymied by a shortage of validated data on the sources of new infections and scaleable prevention approaches, but this is no longer the case. Scientific findings over the past decade have greatly expanded the evidence base for HIV prevention. As Krishnaratne and colleagues observe,4Krishnaratne S Hensen B Cordes J Enstone J Hargreaves JR Interventions to strengthen the HIV prevention cascade: a systematic review of reviews.Lancet HIV. 2016; 3: e307-e317Summary Full Text Full Text PDF PubMed Scopus (84) Google Scholar clear evidence exists of efficacy for voluntary medical male circumcision (VMMC), pre-exposure antiretroviral prophylaxis (PrEP), HIV treatment as prevention, and other biomedical approaches, as well as strong evidentiary support for interventions to increase the supply of condoms, clean needles, and other prevention measures.4Krishnaratne S Hensen B Cordes J Enstone J Hargreaves JR Interventions to strengthen the HIV prevention cascade: a systematic review of reviews.Lancet HIV. 2016; 3: e307-e317Summary Full Text Full Text PDF PubMed Scopus (84) Google Scholar, 5Pickles M Boily MC Vickerman P et al.Assessment of the population-level effectiveness of the Avahan HIV-prevention programme in South India: a prelanned, causal-pathway-based modelling analysis.Lancet Glob Health. 2013; 1: e289-e299Summary Full Text Full Text PDF PubMed Scopus (54) Google Scholar Evidence strongly indicates that the most effective approach to reducing the number of new HIV infections is a combination of biomedical, behavioural, and structural interventions that both reduces vulnerability to HIV acquisition and accelerates uptake of key prevention methods. Despite improvements in HIV prevention science over the past decade, we have yet to see a sufficient decline in new HIV infections. As Dehne and coauthors6Dehne KL Dallabetta G Wilson D et al.HIV Prevention 2020: a framework for delivery and a call for action.Lancet HIV. 2016; 3: e323-e332Summary Full Text Full Text PDF PubMed Scopus (47) Google Scholar explain, current prevention efforts suffer from several weaknesses, including chronic underfunding, variable quality of programme design, the failure to bring interventions to scale, and poor or non-existent monitoring of outcomes. A much stronger, more rigorous approach to HIV prevention, with clearer monitoring and accountability, focused on a single agreed target for reducing new infections, is needed to accelerate the decline in the global HIV burden. Modelling by Smith and co-workers7Smith JA Anderson S-J Harris KL et al.Maximising HIV prevention by balancing the opportunities of today with the promises of tomorrow: a modelling study.Lancet HIV. 2016; 3: e289-e296Summary Full Text Full Text PDF PubMed Scopus (37) Google Scholar indicate that scale-up of existing interventions would strongly accelerate the decline in HIV incidence, but that the public health impact of existing approaches would be magnified by the development and complementary use of newer, easier-to-use technologies that rely less on individual adherence. Synergistic combination of diverse approaches, including structural interventions, is likely to optimise prevention outcomes. Where HIV services have succeeded, programme designers, implementers, and evaluators have used service cascades to clarify key programmatic elements, highlight areas where gaps, or leaks, in the cascade occur, and inform efforts to adapt programmatic design and approaches to improve performance and outcomes. For example, efforts to prevent new HIV infections among children have long benefited from the routine use of data-based service cascades.8Stringer EM Chi BH Chintu N et al.Monitoring effectiveness of programmes to prevent mother-to-child HIV transmission in lower-income countries.Bull World Health Organ. 2008; 86: 1-80Google Scholar, 9Gimbel S Voss J Mercer MA et al.The PMTCT of HIV cascade analysis tool: supporting health managers to improve facility-level service.BMC Res Notes. 2014; 7: 743Crossref PubMed Scopus (22) Google Scholar As the coverage and performance of services to prevent mother-to-child HIV transmission (PMTCT) have improved, the health benefits for children have increased, with 45% fewer children newly infected in 2014 compared with 2009.10UNAIDSTen Targets: 2011 United Nations Political Declaration on HIV and AIDS. Joint United Nations Programme on HIV/AIDS, Geneva2015http://www.unaids.org/sites/default/files/media_asset/20160318_ten_targets_en.pdfGoogle Scholar Indeed, PMTCT efforts, informed by strong data collection and programme monitoring, represent what is arguably the single most important prevention achievement in the history of the epidemic. Cascades have also transformed the HIV treatment agenda. The earliest push to scale up HIV treatment focused almost exclusively on the number of people initiating ART; treatment efforts more recently have routinely monitored outcomes along the HIV treatment cascade, culminating in the ultimate outcome of viral suppression.11Gardner EM McLees MP Steiner JF Del Rio C Burman WJ The spectrum of engagement in HIV care and its relevance to test-and-treat strategies for prevention of HIV infection.Clin Infect Dis. 2011; 52: 793-800Crossref PubMed Scopus (1460) Google Scholar A cascade approach is now the agreed framework for planning and monitoring HIV treatment efforts, as reflected in the UNAIDS 90-90-90 target. Cascades have clear benefits, offering insights to national decision makers and international donors about the return on their HIV investments and how best to allocate resources to close leaks in the cascade and improve ultimate outcomes. A cascade approach also offers advantages at a project level, enabling implementers to identify and address bottlenecks and improve performance over time. Although cascades have been applied most prominently to what are often thought of as biomedical interventions, they also serve to highlight the behavioural and structural factors that influence uptake of and adherence to biomedical regimens, as described by Hargreaves and coauthors.12Hargreaves JR Delany-Moretlwe S Hallett TB et al.The HIV prevention cascade: integrating theories of epidemiological, behavioural, and social science into programme design and monitoring.Lancet HIV. 2016; 3: e318-e322Summary Full Text Full Text PDF PubMed Scopus (98) Google Scholar These include such issues as acceptability, demand, perceived efficacy for self-care, stigma and discrimination, and life challenges (eg, poverty, housing instability, violence) that may impede an individual's ability to adhere to prevention regimens. Garnett and colleagues13Garnett GP Hallett TB Takaruza A et al.Providing a conceptual framework for HIV prevention cascades and assessing feasibility of empirical measurement with data from east Zimbabwe: a case study.Lancet HIV. 2016; 3: e297-e306Summary Full Text Full Text PDF PubMed Scopus (56) Google Scholar applied a cascade approach to a cluster of validated prevention approaches with data in east Zimbabwe to assess the value of this approach. This exercise shows the feasibility of populating an HIV prevention cascade with population-level data to assess the ultimate impact of a prevention intervention and to identify the factors that may prevent the intervention from being used to full effect. In the case of VMMC, for example, the cascade analysis determined that a low perception of risk prevents many men who could benefit from VMMC from accessing the service. This suggests that the health impact of VMMC is unlikely to be maximised without complementary interventions to better motivate men to seek voluntary circumcision. In HIV prevention efforts, the role of evidence-driven programme design, routine data collection and analysis, a clear focus on an agreed target for reducing new infections, and rigorous evaluation of outcomes must markedly increase. As the articles in this issue illustrate, intervention-specific service cascades offer an important avenue to improve the soundness and effect of prevention programmes. Our call to enhance the rigour of prevention programming is urgent, as hopes for meeting our ambitious global goals will only be achieved if treatment-associated reductions in HIV transmission are matched by an equally robust, sustained reduction in HIV acquisition. MTI has received professional fees from the Bill & Melinda Gates Foundation but otherwise declares no competing interest. The remaining authors declare no competing interests. Maximising HIV prevention by balancing the opportunities of today with the promises of tomorrow: a modelling studyWith current information, a strategic approach in which limited resources are used to maximise prevention impact would focus on strengthening the scale-up of existing interventions, while pursuing a workable vaccine and developing other approaches that can be used if further scale-up of existing interventions is limited. Full-Text PDF Open AccessProviding a conceptual framework for HIV prevention cascades and assessing feasibility of empirical measurement with data from east Zimbabwe: a case studyPrevention cascades can be populated to inform HIV prevention programmes. In eastern Zimbabwe programmes need to provide greater access to circumcision services and the design and implementation of associated demand creation activities. Whereas, HTC services need to consider how to increase reductions in partner numbers or increased condom use or should not be considered as contributing to prevention services for the HIV-negative adults. Full-Text PDF Open AccessInterventions to strengthen the HIV prevention cascade: a systematic review of reviewsThere is growing evidence to support a number of efficacious HIV prevention behaviours, products, and procedures. Translating this evidence into population impact will require interventions that strengthen demand for HIV prevention, supply of HIV prevention technologies, and use of and adherence to HIV prevention methods. Full-Text PDF Open AccessThe HIV prevention cascade: integrating theories of epidemiological, behavioural, and social science into programme design and monitoringTheories of epidemiology, health behaviour, and social science have changed the understanding of HIV prevention in the past three decades. The HIV prevention cascade is emerging as a new approach to guide the design and monitoring of HIV prevention programmes in a way that integrates these multiple perspectives. This approach recognises that translating the efficacy of direct mechanisms that mediate HIV prevention (including prevention products, procedures, and risk-reduction behaviours) into population-level effects requires interventions that increase coverage. Full-Text PDF HIV Prevention 2020: a framework for delivery and a call for actionAlthough effective programmes are available and several countries have seen substantial declines in new HIV infections, progress in the reduction of adult HIV incidence has been slower than expected worldwide and many countries have not had large decreases in new infections in adults despite large reductions in paediatric infections. Reasons for slow progress include inadequate commitment, investment, focus, scale, and quality of implementation of prevention and treatment interventions. The UNAIDS–Lancet Commission on Defeating AIDS—Advancing Global Health reported that the provision of large-scale, effective HIV prevention programmes has failed and called on stakeholders to "get serious about HIV prevention". Full-Text PDF