Interventions to Strengthen the HIV Prevention Cascade: A Systematic Review of Reviews

"Much progress has been made in interventions to prevent HIV infection. However, development of evidence-informed prevention programmes that translate the efficacy of these strategies into population effect remain a challenge."

This paper reviews the available evidence for HIV prevention as reflected in systematic reviews of HIV prevention interventions published from January 1995 to July 2015, mapping the evidence base in line with the HIV prevention cascade, describing characteristics of interventions relevant to each area of the cascade, assessing the type of evidence available on these interventions, and identifying gaps and areas for future research. "As the cascade highlights, demand, supply, and use of interventions are all crucial domains to increases in uptake of and adherence to direct HIV prevention mechanisms." The below summary emphasises the communication-related findings from this research endeavour.

From 88 eligible reviews, the researchers identified 1,964 primary studies, of which 292 were eligible for inclusion. They identified primary studies that assessed at least one of: HIV incidence, HIV prevalence, condom use, and uptake of HIV testing. They categorised interventions as those seeking to increase demand for HIV prevention, improve supply of HIV prevention methods, support adherence to prevention behaviours, or directly prevent HIV:

1. The demand-side domain contained studies in which the researchers judged the main aim of intervention to be to influence behaviour by targeting risk perception or strengthening awareness of, and positive attitudes towards, HIV prevention behaviours and technologies. These interventions include those providing information, education, and communication (IEC) and those intended to influence perceived norms through peer-based approaches. Interventions were delivered in a range of settings and to different intended populations. More specifically:
   • 54 primary studies from 40 reviews contributed evidence for IEC interventions (see table 3). The interventions included many different approaches to influence risk perception, awareness, and attitudes about preventive behaviours, including through multimedia, text messages, posters, and other forms of communication. For example, the Helping Each Other Act Responsibly Together (HEART) campaign in Zambia included a multimedia programme of television spots, public service announcements, radio advertisements, music videos, posters, and billboards to share messages about HIV and STI risk reduction. A secondary-school-based programme in KwaZulu-Natal provided sexual health and HIV prevention messages through either drama performances or an information booklet, both delivered in classroom settings. Slightly more than half (56%; n=30) of the IEC studies were of interventions focused on young people. An example is the MEMA Kwa Vijana cluster randomised controlled trial (RCT) of an intervention that provided primary school students with sexual health education through a participatory, teacher-led programme combined with training for health workers to provide sexual health services that are friendly to young people, as well as condom promotion and provision and community mobilisation. Almost all studies of IEC interventions assessed condom use as a primary outcome.
   • 31 reviews contributed 54 studies of peer-based interventions (again, see table 3). Interventions in this category often combined peer-delivered sexual health education with either increased availability of direct mechanisms to prevent HIV, such as condoms, or community empowerment approaches. Studies of interventions designed to reach female sex workers (FSWs) used peer-led community empowerment approaches to support mobilising FSWs and developing a sense of community. An example is a peer-delivered education programme among establishment-based FSWs in the Philippines, which combined venue-manager training with information on HIV and condom use. 12 studies described peer-based interventions among young people. Examples include: (i) a project in Kenya that involved peer educators teaching students about HIV and life skills with songs, quizzes, competitions, and other methods and (ii) Stepping Stones, an intensive community training programme designed for HIV-vulnerable communities in low-income countries. The participatory learning approach sought to empower men and women to take greater control over their sexual and emotional relationships.
2. The supply-side domain contained studies in which the main aim of intervention was judged to be to influence the supply of HIV prevention products and messages. Examples included mass condom distribution, needle exchange initiatives mainstreaming HIV prevention within other services, and treatment strategies for sexually transmitted infections (STIs). In Thailand, the 100% condom-use policy launched in 1989 promoted the practice of "no condom–no sex" in all types of sex work through collaborations between local authorities, sex business owners, and sex workers. Some, but not all, of these interventions have been characterised as structural interventions in published work ("the distinction between the structural and the behavioural has not clearly distinguished interventions...[C]lassifying interventions this way might have created some confusion...").
3. The adherence domain contained studies in which the main aim of intervention was judged to be to support adoption or maintenance of prevention behaviours, including, but not restricted to, the use of prevention technologies. These interventions often sought to influence behavioural self-efficacy or skills and included interventions such as longitudinal risk counselling. More specifically:
   • 26 primary studies described use of counselling alone or with HIV testing to promote HIV prevention. Seven reviews contributed evidence from studies describing couples-based counselling interventions (n=10). One observational study assessed the effect of couples-based counselling on HIV incidence with findings in support of the intervention. Nine studies, including 3 RCTs, assessed self-reported condom use after couples counselling, and findings from these studies were in support of the interventions. Counselling interventions were most often delivered via health facilities through interactions between providers and patients or in community settings by providing either individual, couple-based, or group-based behavioural strategies to reduce HIV risk behaviours. Twelve studies (7 RCTs) assessed individual-level counselling interventions. One example is a programme in South Africa that focused on people without HIV and delivered a 60-min risk-reduction counselling session led by health educators and delivered within a health-care setting. Seven studies (4 RCTs) assessed HIV-positive prevention counselling. For example, an RCT in South Africa studied an intervention that consisted of patient-centred discussions between counsellors and patients living with HIV during regular clinical visits focused on HIV risk reduction and tailored to specific patient needs.

   The researchers also included within this group interventions that targeted social determinants of behaviour hypothesised to act as barriers to the ability of individuals to access or adhere to prevention, such as cash transfers or livelihood interventions. Again, some of these interventions have been identified as structural in the published work.

4. Studies in the direct mechanism domain were most often individually randomised trials of the efficacy of biomedical products or procedures (e.g., pre-exposure prophylaxis (PrEP) or medical male circumcision).

For each specific intervention, they assigned a rating based on the number of randomised trials and the strength of evidence. Primary studies of direct prevention mechanisms showed strong evidence for the efficacy of PrEP and voluntary medical male circumcision. Evidence suggests that interventions to increase supply of prevention methods such as condoms or clean needles can be effective. Evidence arising from demand-side interventions and interventions to promote use of or adherence to prevention tools was less clear, with some strategies likely to be effective and others showing no effect. For example, 98 studies assessing the impact of peer-delivered education programmes on HIV incidence and prevalence among FSWs used experimental and observational designs, but they showed little evidence to support their effectiveness on reducing HIV incidence or prevalence (see table 3). "Findings from demand-side interventions such as information, education, and communication and peer-based interventions on HIV outcomes have been disappointing, with these interventions rarely reducing HIV incidence or prevalence." The quality of the evidence varied across categories.

The researchers explain the implications of their work: "Future research for biomedical tools with demonstrated efficacy should focus on population-level effectiveness. Research on increasing supply of these tools should use more rigorous study designs to measure impact in specific populations, including cluster randomised trials where feasible; if not feasible, a range of alternative impact designs are available. Although a range of interventions seek to address demand for HIV prevention, these have rarely been studied using experimental trials, and, where studied, have shown heterogeneous effectiveness. Similarly, studies of interventions to support use or adherence to HIV prevention need further adaptation and study aligned with the new HIV prevention cascade....Systematic reviews that explore the current evidence in the four categories identified in this paper should be done to understand fully what works, for whom, and under which circumstances. This is an essential next step for the evidence mapping we have initiated here. Future research that builds on the current evidence base and shows approaches to gaining impact for HIV prevention methods is necessary to ensure intervention effectiveness."