What Are Microbicides?

Microbicides are rings, gels, films, or inserts that can kill or neutralize viruses and bacteria. Researchers are studying both vaginal and rectal microbicides to see if they can prevent sexual transmission of HIV. 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 also known as MTN-020, 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.

An ongoing large multinational clinical trial called The Ring Study Exit Disclaimer 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 Institutes of Allergy and Infectious Diseases (NIAID) is moving forward with 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 invited to use the dapivirine ring.

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?

HIV is spread predominantly through sexual transmission. Right now, the best biomedical HIV prevention option for sexually active people is pre-exposure prophylaxis or PrEP. PrEP is a way for people who are at very high risk for HIV to prevent HIV infection by taking a pill every day. When taken every day, PrEP can provide a high level of protection against HIV. However, it is much less effective if it is not taken consistently. While PrEP use is expanding in the U.S., PrEP isn’t widely available globally to those at high risk of HIV.

And even where PrEP is available, it isn’t right for everyone. People who use PrEP must commit to taking the drug every day and seeing their health care provider for follow-up every 3 months. Two major studies of PrEP use by women in sub-Saharan Africa, a region that accounts for 66% of the global total of new HIV infections and where women account for more than half of all people living with HIV, found that participants who used PrEP did not take the study medication daily as prescribed. Daily pills for HIV prevention were not desirable to study participants and did not fit into their lifestyles. Also in the United States and elsewhere, taking a daily pill for HIV prevention is not practical or desirable for everyone. A discreet, long-acting, female-controlled method of prevention such as a microbicide may be a good HIV prevention alternative 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, as they often must do with condoms. Because women and girls are at particularly high risk for HIV/AIDS in many parts of the world, it is especially important to have an effective, desirable HIV prevention tool that women control, such as a vaginal microbicide. Microbicides could make it possible for a woman to protect herself from HIV without his cooperation or knowledge—a particularly important factor for commercial sex workers (prostitutes) or women in abusive relationships. Microbicides might also make it possible someday for women to protect themselves from HIV while still allowing them to get pregnant if they wish.

Rectal microbicides would also give another HIV prevention option for those who engage in anal sex and are not on PrEP, and who are reluctant or unable to use condoms. Many people do not use condoms correctly and consistently for a number of reasons, including personal preference, lack of condom availability, power dynamics in a relationship, and physical and sexual violence.

Can I use a Microbicide to Prevent HIV?

Not yet. The ASPIRE study results are promising—but it will probably be several years before it is known whether regulatory approval is provided and the dapivirine ring is available to the public. Studies of other formulations and forms of microbicides continue and if those clinical trials demonstrate that the microbicides are safe and effective, approval can be sought from regulatory authorities (e.g., the FDA) and the new HIV prevention tools would then be available to consumers.

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

  • PrEP for people who do not have HIV but are at very high risk of getting it.
  • Antiretroviral therapy for people who have HIV, to reduce their risk of transmitting the virus to their sexual partners.
  • 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: 04/19/2016