There has been only a small decline in the prevalence of HIV in the last decade, dropping from 5.9 percent to 5 percent between 2001 and 2009 for those aged 15-49 (UNAIDS, 2010). This decrease, whilst important, does not seem impressive compared to over US$5 billion spent fighting AIDS in low and middle income countries each year (the latest available figure is US$5.1 billion in 2008).

There is a wide variety of HIV prevention interventions including behaviour change communication, biomedical interventions like male circumcision and treatment of sexually transmitted infections, expansion of access to antiretroviral therapy and enhanced prevention of mother-to-child transmission services. Do we know if these interventions work or not?

Behaviour change communication in particular has been considered extremely important given AIDS is a disease that is characterised by ignorance and stigma. Communication therefore seems to have a crucial role in informing, equipping and motivating people to make informed choices about prevention and care.

But the evidence on the effectiveness of behaviour change communication is not good. Systematic reviews, which summarize the available evidence from rigorous impact evaluations, show only a minority of programmes have worked. In one case, only two of nine studies on behavioural interventions showed significant protective effects on HIV incidence among women (McCoy et al., 2009).

What can explain the lack of effectiveness of behaviour change communication?  And what are the implications of this result on our thinking about effective HIV prevention interventions?

Cultural norms and poverty act as barriers to the adoption of safe sex behaviour. “Sugar daddies” in sub-Saharan Africa are an illustration of both these barriers. This is a tradition of sexual reciprocity, where young girls have sex with older men in exchange of money and gifts. Young girls engaging in these relationships do not have much of a choice in negotiating safe sex.

Can structural interventions addressing poverty be a viable approach for HIV prevention? Two recent randomised controlled trials of conditional cash transfers show a significant decline in four sexually transmitted infections (de Walque et al. 2012), and a reduction in HIV infections among adolescent school girls (Baird et al. 2012).

But gender is an important factor in determining impact. Financial rewards can have a negative impact on men. In rural Malawi, conditional cash transfers offered to men led them to engage in more risky sex behaviour (Kohler and Thornton 2011). But when conditional cash transfers were combined with individual and group counselling in Tanzania, the incidence of curable sexually transmitted infections reduced among both young men and women (de Walque et al. 2010).

This initial evidence suggests that structural interventions like conditional cash transfer programmes should be tried and rigorously evaluated to assess if they are viable complements to biomedical interventions. Given that behaviour that is rooted in culture may be harder to change, it is imperative to find interventions that work better.