Our analysis uses a simple, parsimonious model to evaluate the potential impact of MC, and further empirical research is needed to support more detailed models. However, this analysis shows that MC could avert nearly six million new infections and save three million lives in sub-Saharan Africa over the next twenty years. Especially in southern Africa this could go some way to meeting the 2001 United Nations General Assembly Special Session on AIDS targets, the Millennium Development Goals, and the objectives set by bilateral donors, such as the US President's Emergency Plan for AIDS Relief.
Many questions remain to be answered. Better data are needed on the national prevalence of HIV in Africa, as well as on the associated uncertainties. UNAIDS gives plausibility bounds for estimates of national HIV prevalence that are typically about ±30% [
], so the absolute values of the estimates presented here are also uncertain to this extent, although the trends should be more reliable. Better data are also needed on the prevalence of MC in Africa and on the age at circumcision, preferably at the subnational level. Most of the currently available data on the prevalence of MC are several decades old, while several of the recent studies were carried out as adjuncts to demographic and health surveys and were not designed to determine the prevalence of MC [
]. Without such data it is difficult to make reliable estimates of the overall uncertainty in the potential impact of MC on HIV in Africa. Data are also needed on current circumcision practices, especially with regard to safety, on the acceptability of MC, on the cost of MC, and on the feasibility of making it available in places where it is not routinely done. A detailed study is needed of the cost effectiveness of MC as a way of managing the HIV epidemic in Africa using a dynamic model of transmission, accounting for the cost of MC and allowing for the savings that follow reductions in AIDS-related morbidity and the need for ART. In addition, this analysis is based on the result of just one RCT; it will be necessary for the results of that trial to be confirmed before it is clear how accurate these estimates of future infections are.
While the models presented here are a first step towards predicting the impact of MC on HIV in Africa, more detailed models are needed to explore the effect of MC on the age-specific incidence and prevalence of HIV among men and women and on the relative benefits of initially targeting men in certain age groups or in high risk occupations, such as truck drivers or mine workers.
Synergies with other potential interventions, including HIV vaccines, should also be explored, as well as possible synergies acting through the impact of MC on other sexually transmitted infections. Since
for HIV is on the order of 5–10, the 37% reduction in overall transmission associated with MC could make a significant contribution towards reaching the target of reducing
to 1 in the areas where few men are currently circumcised. Combined with other interventions to reduce transmission, this raises the possibility of reducing the prevalence of HIV to such low levels that it is no longer a major public health problem. The impact of MC in South Africa may also be mediated by its impact on other sexually transmitted infections; the results of the other two RCTs of MC, currently being conducted in Kenya [
] and Uganda [
] where the prevalence of other sexually transmitted infections may be different, should throw light on this.
The impact of MC on HIV should also be considered in the context of the increasing availability of ART. To the extent that ART reduces transmission, it will also reduce
and act synergistically with MC. Many studies have shown that ART leads to substantial declines in plasma viral load [
] and may reduce the risk of transmission for those on ART [
]. However, if people in Africa start ART late in the course of their HIV infection, the provision of ART is unlikely to reduce overall transmission significantly [
As a cautionary note, increases in risk-taking behaviour among circumcised men could reduce the benefit of MC. The RCT [
] on which these models are based followed men for an average of 18 months, so that the effects of short-term behaviour changes have been accounted for. Community or population level studies of MC are now needed to determine the likelihood of behavioural disinhibition and to assess its impact on transmission in the long term.
While MC confers greater direct benefits on men than on women, women benefit indirectly through the reduction in the prevalence of HIV among their male sexual partners. Nevertheless, it is already the case that in Africa more women than men are infected with HIV [
], and additional methods that help to protect women, such as the development of effective vaginal microbicides, are still needed. A trial under way in Uganda [
] has been designed to measure the impact of MC on male-to-female transmission of HIV.
The earlier observational studies and the recent RCT all suggest that MC will have a long-term, population-level impact on HIV transmission. However, this assumption needs to be tested at the population level, and a large-scale, community-based programme to implement MC as widely as possible should be implemented and carefully monitored to determine the population level impact of MC directly.
This analysis makes it clear that MC could have an immediate impact on HIV transmission, but the full impact on prevalence and deaths will only be apparent about ten to fifteen years later. The reason is that circumcision averts infections some years into the future among people who would have died ten years later, on average. The same argument applies, of course, to other prevention methods because reductions in illness and death will only be manifested a decade or more after their introduction. The need to keep HIV-positive people alive through the provision of ART remains the most immediate priority while ways are found to reduce transmission using MC and other interventions.