With funds devoted to HIV/AIDS declining, there has not been a better time, at least in the past decade or so, to optimize the use of the limited resources between treatment and prevention. In the wake of HPTN 052, which found that treating HIV-infected partners in mostly heterosexual HIV-discordant couples can practically eliminate HIV transmission to the HIV-negative partner, the debate over whether and how much of the funds should be devoted to prevention has become even more salient (I wrote about this earlier here). If the study findings are replicated elsewhere for other populations, it is clear that treating people living with HIV is also prevention to the extent that they’re sexually active with HIV-negative individuals.
However, it is also clear that governments, even richer ones let alone those in Africa, are not going to adopt early treatment regimes anytime soon. Without going into detail, there are good reasons for this: the most infectious people are those in the late stages of the disease, i.e. eligible for treatment anyway; we don’t know the long-term effects of treating people with ARVs; starting treatment earlier does not provide substantial benefits to the treated person (he/she would be taking medication for his/her sexual partners); and practicality of ‘test and treat’ for the entire population. While these get sorted out, we still need to try to prevent people from becoming infected with HIV.
What do we know so far on what works in HIV prevention? We have more or less figured out prevention of transmission from mother to child. This does need to become a regular part of prenatal care, but it won’t affect sexual transmission rates. We now also have good evidence that voluntary medical male circumcision works (longer term studies have not yet found any significant disinhibition effects, meaning the protective effect is persisting over the longer term), but many countries need to roll it out to reach the masses. There are both supply and demand-side issues that need to be tackled and I will be writing more about this in the upcoming weeks. Vaccine development continues, so does research on the effectiveness of pre-exposure prophylaxis (remember the microbicidal gel trials successful in Phase 2 but failing in Phase 3?), neither of which have yet been proven to be effective. Treating other STIs, such as HSV-2, does not seem to be effective either – even though there are biological reasons to think it should be.
Moving away from the biomedical prevention methods to behavior change programs, the picture is dismal. A recent review by Nancy Padian and colleagues finds not a single intervention showing a decline in HIV incidence as a result of a behavior change intervention. The authors point to the fact that lack of statistical power to detect meaningful declines may have been a factor in these studies. Regardless, this puts the funding agencies in a bind: what to do with interventions that try to promote abstinence, condom use, being faithful – the ABC approach that was touted heavily until recently? We have no evidence that they work. Yes, it is possible that there are some approaches that have not been tried which might work, but should we keep banging our heads trying to make ABC work? Or, is it time to start looking elsewhere?
To the proponents of behavior change interventions, there is a mirage: there has been some decline recently in HIV incidence in Sub-Saharan Africa. DHS data are also showing some signs of (self-reported) behavior change, especially among young people. So, the thinking goes, these two things must be linked. Perhaps, but that does not mean that the causality went from behavior change programs to behavior change to decline in HIV incidence. It could also be that it went from high HIV incidence to behavior change to lower HIV incidence – with behavior change programs making implementers feel good but doing nothing to prevent new infections.
That behavior change might be happening in response to the intensity of the HIV epidemic and the competing disease risk gets support from a paper by Emily Oster just published in the Journal of Health Economics. Using an IV strategy, she finds that increased HIV rates lead to lower rates of unprotected sex with multiple partners and that this response varies by non-HIV life expectancy. She finds no evidence that lack of knowledge about HIV is a factor in behavior change.
Given that biomedical solutions are still distant, there is no doubt that we’ll continue to try other prevention strategies – including behavior change interventions. However, we owe it to ourselves to (a) not keep trying the same things; and (b) design evaluations properly (i.e. pointing to the channels rather than combination packages) and with sufficient power to either show effects or convince us of that the null effect is real. Funding agencies should apply extra scrutiny to proposals with behavior change interventions.
Of course, our behavior responds to all sorts of other things, such as income, aspirations, competing disease risks, equity, etc. These are domains that have not been traditionally in the HIV prevention field. Perhaps they deserve a harder look, at least a place on the table, and I plan to talk more about the potential of these ‘structural’ factors in the upcoming weeks.