Despite decades of intense research searching for an effective HIV vaccine, the best prevention strategy we have right now is strikingly simple: use a condom. Unfortunately, this is not always an option for women in societies where men hold the decision-making power, even when it comes to women’s bodies. With this in mind, a major goal of HIV prevention research is to give women a way to protect themselves.
One focus of such research has been on developing a microbicide, an antiviral gel that a woman can apply vaginally before or after sex, even when her partner is unwilling to use a condom. However, 20 years and 11 clinical trials of candidate microbicides have failed to show any protection (take a look at this timeline of microbicide development). With decades of disappointment highlighting how difficult it is to stop HIV, promising preliminary results from a CAPRISA (Centre for the AIDS Programme of Research in South Africa) trial indicate that this finally might be changing.
In this trial, women who used the microbicide gel showed a 39% lower HIV incidence than those who did not, and for women who used the gel consistently there was a 54% decrease. Although the study included only a small sample of women, and the level of protection was not nearly as good as that offered by a condom, the idea that research is headed in the right direction is certainly inspiring. In fact, after the presentation of the results at last year’s international AIDS conference in Vienna, the entire room took to their feet for several minutes of applause. The researchers estimate that, after more studies to confirm and extend their findings, this gel has the potential to prevent 1.3 million new infections and more than 800,000 deaths over the next 20 years in South Africa alone.
The results of this trial make it clear that this is a strategy worth pursuing. And, thinking about why this particular microbicide showed such promising results while previous trials did not should offer insight into how to make this strategy suitable for use outside of a clinical trial. One difference in the CAPRISA trial was that they started with a drug already known to work: tenofovir, which is currently used to treat people infected with HIV and to prevent infected pregnant women from transmitting HIV to their babies.
One big idea in many of these trials is “proof of concept.” This basically means that, while the drug or strategy tested is not ready to roll out to the general population, the trial shows that the idea is sound and it is likely that further testing will help refine it. So, while this might not be the big breakthrough we’ve been waiting for yet, someday it might be. (Here are some more details on CAPRISA and other HIV prevention studies.)