HIV prevention for South African youth: which interventions work? A systematic review of current evidence

With South African youth aged 15-24 experiencing among the highest HIV prevalence in the world [1], the development of effective HIV prevention programmes is a top public health and policy priority [2]. However, in spite of recent calls to increase attention to the high levels of HIV transmission to young women [3], particularly in southern Africa [4], little scientific consensus exists about how best to prevent HIV infection among youth. In countries where HIV prevalence has declined at population level, sexual behaviour change among young people has been cited as an important contributing factor [2]. Yet questions remain regarding how to achieve - and maintain - the individual-level behavioural changes needed to reduce HIV incidence.

Comprehensive sexuality education is considered an important means of addressing adolescent risk behaviours [5, 6], although little evidence supports its direct impact on biological measures of prevention success, particularly HIV and other sexually transmitted infections (STIs) [5–7]. In sub-Saharan Africa, experience with youth HIV prevention programmes is limited, with evidence regarding effectiveness still emerging. Recent trials of youth HIV prevention interventions have achieved mixed results. Three large community trials of comprehensive approaches to youth HIV prevention, involving schools and other key institutions and stakeholders, have failed to significantly reduce HIV incidence in young people, and have shown only modest success in increasing protective behaviours [8–10]. However, two group-based interventions in South Africa have shown promise in reducing reported HIV-related risk behaviours, and in one case, associated biological outcomes [11–13]. Both interventions addressed HIV-related structural factors, or the social influences underlying HIV risk [14], namely gender-based violence [11–13] and women's poverty [12, 13]. Together with limited results of several smaller, school-based interventions, these outcomes have triggered debate about 'which interventions work' [15].

Prior reviews of youth intervention studies in both developed and developing countries [2, 5, 7, 16–19] suggest an important role for school-based interventions in increasing young people's knowledge of sexuality, reproductive health, and HIV prevention, with a majority leading to reductions in reported risk behaviours [5]. Reviews of school-based interventions specific to sub-Saharan Africa have found greater intervention impact on HIV-related knowledge and attitudes than on reported sexual behaviours [16, 17], a finding reinforced by two recent large-scale trials in Tanzania, the Mema kwa Vijana (MkV) Project, and Zimbabwe, the Regai Dzive Shiri (RDS) Project [9, 10]. These trials impacted knowledge and attitudes (both), self-efficacy (RDS), some aspects of men's sexual behaviour (MkV), and also self-reported pregnancy (RDS). Lessons learned from these trials include the need to change population norms regarding sexual risk behaviours, and to address a broad range of interpersonal, cultural and structural factors underlying HIV risk [20]. Further, strengthening and broadening existing approaches, like school-based programmes, and adopting new approaches to reduce youth HIV incidence in sub-Saharan Africa are important [16, 17, 20].

To understand current evidence for youth HIV prevention in sub-Saharan Africa, and to answer the question 'which interventions work, and why', reviews of intervention content and characteristics of successful interventions are needed. While several systematic reviews of HIV prevention interventions have included developing country adolescents [2, 5, 16–18, 21], only three focused on sub-Saharan Africa specifically [16, 17, 21]. Two reviews included only school-based studies [16, 17], while the third reviewed studies with an HIV endpoint [21]. Further, many reviews primarily consider methodological and study design issues [16–19]. Reviews may include few details about interventions, or on secondary and process outcomes that indicate pathways to intervention outcomes. Lastly, since systematic reviews are often based on published studies, recently-completed studies may be excluded, although these may offer relevant lessons learned, helping to identify promising approaches.

The debate about 'which interventions work - and why' has been renewed following recent trial results. In South Africa, the continued severity of the HIV epidemic has lent new urgency to these questions - and their answers [22]. The development of interventions specific to the South African context is an urgent research priority [23], and may support intervention approaches for sub-Saharan Africa more broadly. To inform the development of an evidence-based, state-of-the-art approach to youth HIV prevention in South Africa, we undertook a review of ongoing or recently completed intervention studies, with the aim of systematically assessing characteristics of rigourously designed youth HIV prevention interventions, to better understand how they work, and why.

This review addresses study design, intervention design, including content and theoretical basis, thematic focus and HIV causal pathways, and intervention delivery and implementation, among youth aged 12-24 years in South Africa. The review methodology was adapted from other reviews of adolescent HIV prevention studies, to ensure rigorous and systematic assessment of the strength of evidence on intervention effectiveness [2, 5, 18, 19, 23].

How do the findings from this review answer the question 'what works' to prevent HIV infection in young people in southern Africa? Importantly, the review identifies key elements associated with intervention impact, and highlights promising approaches in youth HIV prevention for South Africa and similar settings. These eight interventions, most of them rigorously designed with regard to intervention and evaluation, indicate progress toward improved HIV prevention, based on behavioural proxy measures for HIV infection. However, given the range of interventions that have been tested, differences in the relative strengths and weaknesses of evaluation designs, and the limited effectiveness of many interventions, a definitive assessment of 'what works' is not possible. Yet important lessons are learned, leading to specific recommendations for future research.

What are the lessons learned from the eight studies included in this review? First, moving beyond individual-level measures of knowledge and psychosocial factors to address social and structural factors underlying HIV risk is the main success of these interventions. An important feature - and their area of greatest impact - was the focus on HIV causal pathways relevant to southern Africa, namely gender, sexual coercion, alcohol use and economic risk. Results of the two other major youth intervention trials in sub-Saharan Africa, MkV and RDS, support the importance of addressing social and institutional, as well as individual level, factors to change population-level norms about HIV risk behaviours [9, 10, 21]. However, addressing social factors is not the same as implementing a 'structural intervention', as in the IMAGE project where women's access to economic resources apparently increased personal empowerment, leading to reduced sexual risk behaviour [42], a finding observed in the larger trial as well as the sub-group of younger women. Similarly, Stepping Stones led to changes in gender beliefs and values, thus impacting the structural context of risk [11]. An important second lesson, then, is the need for interventions to adopt structural approaches that can alter the context of young people's HIV risk. Although structural interventions are often critiqued as 'social development' rather than focused health interventions [14], in fact these studies offer several important examples of how targeted structural approaches can change individual behaviour. The HealthWise intervention offered young people alternatives for leisure time use, while in the Adolescent Livelihoods project young people learned life skills, such as numeracy, that may enhance vocational and educational success. Promising economic interventions are also being tested in other sub-Saharan African settings [43]. Third, changing social norms related to HIV risk and protective behaviours is important. Stepping Stones' success was clearly associated with altering beliefs about gender and HIV risk, particularly among men, and with offering viable alternative normative behaviours [11, 44]. One way that group intervention approaches, such as IMAGE and Stepping Stones, generate positive social norms is through engaging participants in collective critical thinking, thereby fostering self-esteem and individual empowerment [45]. Community mobilisation, employed effectively among women in the IMAGE project and in other promising interventions [13, 14, 45], is also an important component. Importantly, most school-based interventions do not use a group approach, but are delivered didactically by teachers in classrooms, relying on the ability of students to act individually on information received. A simple way to address this would be for school-based interventions to include more group-based, rather than didactic, learning. A fourth lesson learned is thus the need to engage schools differently in HIV prevention, including use of personnel other than teachers to deliver interventions. While peer education is popular among students, this review supports other findings that offer little evidence for its ability to increase intervention impact [46, 47]. One approach with certain advantages over teachers, who often resist teaching sexuality education, and same-age peers, who may sometimes have difficulty commanding the necessary authority to run a classroom [41, 47], would be to use older youth as 'mentors'. School mentors could work in partnership with teachers who request to teach sexuality education and HIV prevention, but would relieve the reliance on teachers who do not want this responsibility.

Of the five school-based interventions reviewed, four experienced serious implementation problems, leading to calls for interventions to target the school level as well as individual students [31, 32, 34]. Interventions in South African schools experience challenges to fidelity, due to scheduling disruptions, high levels of student and teacher absenteeism, frequent violence and other school-level issues [48]. These findings thus suggest the need to change how school interventions are implemented, with enormous potential to improve on current models. Yet in spite of the difficulties, schools have some important advantages for intervention delivery, including the ability to reach a large number of youth [49, 50], suggesting that working to improve school-based intervention models is an important priority. Methods from the education sector could inform HIV prevention interventions, including the use of school mentors, teacher training in participatory learning approaches, and efforts at school-level change [48]. At the same time, recognition of the considerable variation in youth needs is important, and interventions in community or other venues designed to reach out-of-school youth, or older adolescents, are also research priorities.

Based on the findings from this review - and from the MkV and RDS trials - specific recommendations for a 'third generation' of youth HIV prevention interventions can be made. These include 1) conducting trials of youth-focused structural interventions, with the aim of altering the structural context of HIV risk; 2) developing new approaches for schools, including interventions that target school-level factors and engage schools as active partners, including mobilising the broader 'school community' of students, teachers, parents and community members; and 3) ensuring that future trials have better measurement and more rigorous designs, including HIV incidence - or another comparable biological measure, such as HSV-2 - as the primary outcome, as well as longer-term follow-up. These recommendations can help to address remaining gaps in knowledge about youth HIV prevention, in spite of important lessons learned from the 'second generation' interventions reviewed here. These include a more definitive understanding of the merits of multi- versus single-component interventions, or of broad-based versus more narrowly targeted approaches, and developmental considerations, like age, gender, sexual activity, and schooling status. These recommendations can help to improve youth HIV prevention research, where - in spite of great progress - no interventions have yet demonstrated a reduction in HIV incidence. This remains the most important - and essential - marker of intervention success.