An Important Success in HIV Prevention Research – and the Need for a Lot More Work
July 28, 2010
Senior Associate, Global Health Policy Center, CSIS
The widely celebrated results of the vaginal microbicide study announced last week in Vienna are an important first step in the search for an HIV prevention method that can be controlled by women for effective prevention of sexual transmission. The parallel tasks at hand now are to continue moving forward to collect the data needed to confirm and extend the recent study results and to begin thinking through the many practical and logistical steps required to make an effective microbicide widely available.
The placebo-controlled study, conducted by the Centre for AIDS Prevention Research in South Africa (CAPRISA) in collaboration with Family Health International and the University of North Carolina , has demonstrated that a vaginal gel containing a 1% preparation of the anti-retroviraL drug tenofovir could reduce sexually active women’s risk of becoming infected with HIV. The study, called “CAPRISA 004,” found an overall HIV risk reduction of 39% among those women who adhered to the microbicide gel recommendations for use both before and after intercourse. Investigators also saw a clear and convincing “dose-response” effect, with those who used the gel as recommended >80%, 50-80% and <50% of the time having HIV risk reductions of 54%, 38% and 28% respectively. Some of the background data for the study can be found here.
Although these results of this single study are ground-breaking and exciting, a lot more information will be needed before recommendations can be made for the widespread use of such a microbicide gel. The results presented in Vienna need to be confirmed by at least one more study; one such study, sponsored by NIH, is already underway. Later results from the CAPRISA study itself will eventually indicate whether the prevention effect of the gel lasts beyond the 24 months covered by the study. In addition, the NIH-sponsored study will provide information on whether other regimens of using different doses of tenofovir can provide the same or different HIV risk reductions and will hopefully confirm the absence of clinically important side effects of long term tenofovir use. The NIH-sponsored study, known as VOICE is also investigating the use of orally administered tenofovir and another oral anti-retroviral drug to prevent sexual transmission of HIV.
In anticipation of good confirmatory study results, UNAIDS is creating an expert group to begin crafting recommendations for widespread use of tenofovir and other microbicides in various kinds of sexual exposure situations.
Assuming that these steps all work out as planned, the final step will need to be a careful assessment of community-level HIV prevention results of the use of the recommended microbicide gel in one or more communities. This last step is needed to be sure that the study’s HIV prevention results observed in intensive research settings such as CAPRISA 004 and VOICE are maintained in community-based microbicide use, when less support is available for adherence to recommendations for use.
All in all, the CAPRISA 004 results give great hope to those waiting for another biomedical breakthrough in the HIV prevention field. However, the importance of existing and already proven behavioral and biomedical HIV prevention strategies needs to be kept in mind as the basis of a comprehensive and combined HIV prevention package.