HIV prevention cascades: A unifying framework to replicate the successes of treatment cascades

Abstract

Many countries are off track to meet targets for reducing new HIV infections. HIV prevention cascades have been proposed to assist in the implementation and monitoring of HIV prevention programmes by identifying gaps in the steps required for effective use of prevention methods, similar to HIV treatment cascades. However, lack of a unifying framework impedes widespread use of prevention cascades. Building on a series of consultations, we propose an HIV prevention cascade consisting of three key domains of motivation, access, and effective use in a priority population. This three-step cascade can be used for routine monitoring and advocacy, particularly by attaching 90-90-90-style targets. Further characterisation of reasons for gaps across motivation, access, or effective use allows for a comprehensive framework, guiding identification of relevant responses and platforms for interventions. Linking the prevention cascade, reasons for gaps, and interventions reconciles the different requirements of prevention cascades, providing a unifying framework.

Figure 1:. A generic and unifying HIV prevention cascade framework.: A: The core steps of the cascade of motivation to use the prevention method, access to it, and effective use of it in a priority population that would benefit from use of the prevention method. B: The complete cascade that shows the gaps in the cascade across motivation, access, and effective use, and major reasons underlying these gaps. The displayed reasons do not represent an exhaustive list and, although some of these reasons are likely to be widely applicable, they may differ in relative importance between settings, populations, and prevention methods. The reasons provide links to interventions and platforms for interventions to improve motivation, access, and effective use in the priority population.

Figure 2:. HIV prevention cascades following the models proposed by Garnett et al. for condom use among males in Manicaland, Zimbabwe, 2012-2013.: The cascades show the number of HIV infections not prevented due to gaps in different cascade steps for males (aged 15-54) who reported sexual activity in the past two weeks and at least one sexual behaviour associated with increased risk for HIV infection (multiple, casual, or concurrent sexual partners), with HIV incidence estimated from the 2009-11 and 2012-13 Manicaland Study surveys (1.43 per 100 person-years). A: User-centric cascade with risk perception referring to reporting perceiving a risk for HIV infection in the future. B: Provider-centric cascade with availability referring to reporting knowledge of a place where condoms are available locally. Uptake was using a condom at least during one sexual encounter in the past two weeks. Consistent use was using a condom during every sex act in the past two weeks. Efficacy of 80% was assumed. Data on cascade steps were taken from the 2012-13 Manicaland Study survey. See supplementary material for details on data and methods.

Figure 3:. HIV prevention cascades following our proposed model for condom use among males and females in Manicaland, Zimbabwe, 2012-13.: The priority populations were HIV-negative males (A) and females (B) (aged 15-54) who were reported sexual activity in the past two weeks and at least one sexual behaviour associated with increased risk for HIV infection (multiple, casual, or concurrent sexual partners). Individuals were classified as motivated if they reported perceiving a risk for HIV infection in the future. Among those classified as motivated, individuals were classified as having access if they reported knowing a place where condoms are available locally. Among those classified as having access, individuals were classified as effectively using condoms if they reported using a condom during every sex act in the past two weeks. Numbers are percentages of the priority population. See supplementary material for details on data and methods.