What Are Microbicides?

Microbicides are experimental products containing drugs that prevent vaginal and/or rectal transmission of HIV and/or sexually transmitted infections. Researchers are studying microbicides delivered in the form of vaginal rings, gels, films, inserts and enemas. A safe, effective, desirable, and affordable microbicide against HIV could help to prevent many new infections.

Can Microbicides Prevent HIV Infection?

The answer to this question now appears to be “Yes, to a modest degree.”

Several large-scale research studies over the past decade have investigated the safety and effectiveness of different microbicides.

In 2016, results from the NIH-funded ASPIRE study, a large clinical trial conducted at 15 clinical research sites in Malawi, South Africa, Uganda, and Zimbabwe, showed that a vaginal ring that continuously releases the experimental antiretroviral drug dapivirine provided a modest level of protection against HIV infection in women. The ring reduced the risk of HIV infection by 27 percent in the study population overall and by 61 percent among women ages 25 years and older, who used the ring most consistently.

A second clinical trial called The Ring Study Exit Disclaimer conducted in parallel with the ASPIRE study also tested the dapivirine ring for safety and efficacy in women. Similar to ASPIRE, The Ring Study investigators found an overall effectiveness of 31 percent, with a slightly greater reduction in risk of HIV infection among women older than 21 years.

To build on the findings from these studies, NIH’s National Institute of Allergy and Infectious Diseases (NIAID) is funding an open-label extension study of the vaginal ring to see if this experimental product can offer increased protection against HIV in an open-label setting in which all participants are counseled on how effective the ring may be, and are invited to use or not use the dapivirine ring in order to yield insight into why some women may choose to use or not to use the ring. Finding HIV prevention options that are acceptable to women and that can be integrated into their daily lives is a critical component of developing prevention strategies that work for diverse populations.

Other studies Exit Disclaimer are examining potential rectal microbicide gels to reduce the risk of HIV transmission through anal sex. Some are testing microbicides originally formulated for vaginal use to determine if they are safe, effective, and acceptable when used in the rectum; others focus on the development of products designed specifically for rectal use.

Learn more about prior microbicides studies and NIAID’s ongoing research on both vaginal and rectal microbicides.

Why Are Microbicides Important?

The only currently licensed and available biomedical HIV prevention product comes in the form of a daily pill taken orally (tenofovir-emtricitabine sold as Truvada®), and is called pre-exposure prophylaxis, or PrEP. But protection from it requires consistent, daily use. A daily pill can be challenging for some people to take, so other forms of biomedical HIV prevention are being explored.  A discreet, long-acting, female-initiated method of prevention such as a microbicide may be a good HIV prevention option for some women.

Microbicides may also be preferable to condoms as an HIV prevention option for some women because women would not have to negotiate their use with a partner, as they often must do with condoms. Because women and girls are at particularly high risk for HIV in many parts of the world, it is especially important to have an effective, desirable, woman-initiated HIV prevention tool. Microbicides could make it possible for a woman to protect herself from HIV. In the future, it may be possible to formulate products that combine anti-HIV microbicide agents with contraception.

Rectal microbicides would also offer another HIV prevention option for men or women who engage in anal sex.

Can I Use a Microbicide to Prevent HIV?

Not yet. The ASPIRE study results are promising, but further study is needed, along with approval by drug regulators before the vaginal ring can be used by the public. Meanwhile, research on other formulations and forms of microbicides continues.

For now, available forms of protection against sexual transmission of HIV continue to be:

  • Antiretroviral therapy for people who have HIV, to reduce their risk of transmitting the virus to their sexual partners (i.e., treatment as prevention)
  • Daily PrEP
  • Voluntary medical male circumcision
  • HIV testing—so that you know your own HIV status and your partner’s, too.
  • Using condoms consistently and correctly.
  • Choosing less risky sexual behaviors.
  • Reducing the number of people you have sex with.

The more of these actions you take, the safer you will be. To learn more, see Lower Your Sexual Risk for HIV.

Prevention Research

Vaccines Microbicides

Last revised: 05/25/2017