Examining the Promise of HIV Elimination by 'Test and Treat' in Hyperendemic Settings

Peter J. Dodd; Geoff P. Garnett; Timothy B. Hallett

Disclosures

AIDS. 2010;24(5):729-734. 

In This Article

Abstract and Introduction

Abstract

Background: It has been suggested that a new strategy for HIV prevention, 'Universal Test and Treat', whereby everyone is tested for HIV once a year and treated immediately with antiretroviral therapy (ART) if they are infected, could 'eliminate' the epidemic and reduce ART costs in the long term.
Methods: We investigated the impact of test-and-treat interventions under a variety of assumptions about the epidemic using a deterministic mathematical model.
Results: Our model shows that such an intervention can substantially reduce HIV transmission, but that impact depends crucially on the epidemiological context; in some situations, less aggressive interventions achieve the same results, whereas in others, the proposed intervention reduces HIV by much less. It follows that testing every year and treating immediately is not necessarily the most cost-efficient strategy. We also show that a test-and-treat intervention that does not reach full implementation or coverage could, perversely, increase long-term ART costs.
Conclusion: Interventions that prevent new infections through ART scale-up may hold substantial promise. However, as plans move forward, careful consideration should be given to the nature of the epidemic and the potential for perverse outcomes.

Introduction

The rate of new HIV infections has stabilized in recent years (2.7 million infections in 2007[1]), and concomitantly, the global number of those infected on antiretroviral therapy (ART) has increased dramatically.[2] Despite this, the rate of new infections in developing countries still outpaces the rate at which individuals are started on treatment,[2] and there is growing concern that this situation is unsustainable.[3,4] Incidence must be further reduced, but disappointingly, few HIV interventions have been shown to be effective in randomized controlled trials in developing countries: behaviour changes following counselling and testing are likely to have a minimal effect or even increase incidence;[5,6] two models of peer education for promoting reductions in risk behaviour have failed;[7,8] risk compensation and low adherence potentially contributed to no effect being found in trials to prevent HIV infection through diaphragm use[9] and herpes treatment;[10] and, in the last year, another trial of herpes treatment showed no effect on the rate of HIV transmission from coinfected individuals.[11] These results bring the tally of trials showing no efficacy in reducing HIV incidence to more than 30.[12] Male circumcision has been shown to reduce the risk of men acquiring infection,[13–15] although it is understood that this will not be enough to eliminate HIV, even under the most optimistic conditions.[16,17]

In contrast, scale-up of ART has substantially reduced mortality.[2,17–19] As the availability of treatment expanded, Montaner et al.[20] proposed using treatment as an intervention to prevent infection, and Granich et al.[21] recently used a mathematical model to evaluate that argument. The model suggested that in a high prevalence setting, with an incidence of two per 100 person-years at risk, an intervention that tested everyone annually and initiated treatment immediately if they were infected ('universal test-and-treat' intervention) could reduce incidence to below one per 1000 person-years at risk, that is, more than a 95% reduction (described by the authors as elimination). The model predicted that despite high costs during the rollout phase, long-term ART costs would be much lower than the current strategy of treating on the basis of clinical need.

This result has stimulated extensive comment and sparked interest in rolling-out 'test-and-treat' type interventions.[22–28] However, it is worth further exploring the findings, as the model provided a limited representation of some aspects of HIV epidemiology and investigated only one type of intervention in one type of epidemiological context. In this article, we investigate the potential of alternate test-and-treat interventions under a range of contexts, and using a different mathematical model that incorporates updated information on the course of HIV infection and transmission rates on treatment along with a more explicit exploration of the potential role of heterogeneity in sexual risk behaviour.[29,30]

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