More people than ever have access to effective AIDS treatments. But the virus will never be contained without more effective measures to prevent transmission — and the need for measures that can be initiated by women is especially urgent.

Unfortunately, the run-up to this year's International AIDS Society (IAS) conference in Sydney, Australia, has been dominated by negative research results concerning female-initiated prevention. But scientists and advocates should keep working resolutely together to make sure that testing of such methods continues apace.

The vast majority of new HIV infections in Africa, where the pandemic is most severe, occur through heterosexual transmission. But women are often powerless to negotiate the use of condoms — by far the best way to prevent infection. This is the impetus behind the clinical trials now testing alternative female-initiated prevention techniques. These include microbicides — gels or creams applied to the vagina to block infection; barrier methods, such as diaphragms; and methods that can be used by both men and women, including preventative drugs.

It has been a long, difficult slog to get any of these methods into effective field trials, making the recent negative results doubly disappointing. In January, two trials of the microbicide cellulose sulphate were stopped when an interim analysis suggested that the product might make women more vulnerable to HIV. The product was the third microbicide to fail in efficacy studies and the second that seemed to increase the risk of HIV. And on 12 July, a team of researchers in South Africa, the United States and Zimbabwe reported that latex diaphragms used with condoms did not protect more women from HIV than condom use alone. On 25 July, investigators of the failed cellulose sulphate trials are expected to unveil their final data analysis at the IAS meeting — a step that will very probably spell the end for that particular product.

Women, vaginas and sexuality are not topics that government officials want to air in public.

Looking forward, there is tension in the field over how best to conduct the next microbicide trials (see Nature 448, 110–111; 2007). The danger is that further bad news will see funders lose their appetite for research on female-initiated prevention methods, so there is tremendous pressure to avoid more failures. This field has always been a difficult sell for policy-makers in any case: as long-time advocate Lori Heise of the Global Campaign for Microbicides says, it's about “women, vaginas and sexuality” — not topics that government officials especially want to air in public.

But developing and testing such measures will take a long time. There is no HIV vaccine in sight, either, but researchers seldom consider abandoning the quest for one. Product development is even more difficult than usual for female-initiated prevention methods, because testing them requires dealing with issues related to intimacy, cultural expectations and interpersonal relationships. It is hard for researchers to navigate these types of issues. Some see a more thorough investigation of all the circumstances surrounding a proposed intervention as a way around this. In a declaration circulating ahead of the Sydney meeting, which begins on 22 July, hundreds of scientists are calling for 10% of all HIV programme funds to be dedicated to such approaches.

But there is already a paucity of funding for proven prevention methods, according to a June report by the Global HIV Prevention Working Group. And a study released last week found that large-scale prevention programmes are the most cost-effective (E. Marseille et al. BMC Health Services Res. 7, 108; 2007). It is clear that more resources should be directed at delivering the methods that work and at improving communication with the communities involved, to ensure both that existing prevention methods are used and that future trials will be conducted in optimal circumstances.

Dedicated researchers already know this. The principal investigators for a trial of a new microbicide gel containing the antiretroviral drug tenofovir, for instance, had extensive discussions with women before setting the dosing schedule for their drug. Such preparation is just as important as continued support for the search for good, female-initiated HIV prevention methods. With dedicated work on both fronts, researchers and advocates can be confident of finding the solutions that will control the pandemic and help women stay healthy.