PrEP for Women
March 1, 2017
Table of Contents:
- What Is PrEP?
- How Does PrEP Prevent the Spread of HIV?
- Approval for Daily Oral PrEP
- Has PrEP Been Shown to Be Effective?
- Why Are Some Research Findings Unclear?
- CDC and WHO Guidelines for PrEP Use
- The PrEP Debate
- What Does PrEP Mean for Women?
- Considering Taking Truvada as PrEP?
- New Developments in the PrEP Arena
PrEP stands for Pre-Exposure Prophylaxis. It means taking medicine before being exposed to something to prevent yourself from getting a disease or condition. We use several kinds of medicine this way.
One example is taking anti-malaria medication when we travel to areas where we might be bitten by mosquitoes that carry malaria. When the medicine is in a person's body before getting a mosquito bite, that person is much less likely to get malaria when she or he is bitten.
For women, another example is taking birth control pills (contraceptives). When contraceptives are already in a woman's body when she is exposed to semen during sex, her chances of getting pregnant are greatly reduced.
When we talk about PrEP in connection to HIV and women, we are referring to the idea of HIV-negative women taking HIV drugs to reduce their risk of becoming HIV-positive if they are exposed to the virus. Some people use the term "topical PrEP" to describe the use of microbicide gels (e.g., vaginal gels containing HIV drugs). However, in this article when we talk about PrEP, we are referring only to "oral PrEP," or HIV drugs taken by mouth as prevention.
Here is how PrEP works:
- When CD4 cells are infected with HIV, they become little factories that make thousands of new viruses each day
- HIV drugs work by blocking HIV from making copies of itself
- If an HIV-negative woman already has HIV drugs in her bloodstream when she is exposed to HIV during condomless sex, for example, the medicine might be able to keep the HIV from making enough copies of itself to "take hold" and prevent her from becoming infected
Based on the findings of studies mentioned below, in July 2012, the U.S. Food and Drug Administration (FDA) approved the daily use of Truvada (tenofovir disoproxil fumarate plus emtricitabine, or TDF/FTC) as PrEP for sexually active adults at risk of HIV infection. Truvada is a drug often used as part of combination drug treatment for HIV. This is the first time the FDA has approved any drugs for the prevention of HIV.
The U.S. Centers for Disease Control and Prevention (CDC) estimates that meeting the testing, treatment, and PrEP targets established by the National HIV/AIDS Strategy could prevent 185,000 new HIV infections in the U.S. by 2020. If testing and treatment rates remained the same over the next few years, researchers predict expanded PrEP coverage alone could reduce new infections by 20 percent.
The World Health Organization (WHO) released updated guidelines in June 2016 expanding earlier recommendations that daily oral PrEP be offered as an additional prevention method for all people at substantial risk of getting HIV. The WHO approves either Viread (tenofovir disoproxil fumarate) or Truvada for daily oral PrEP.
Each country must approve the use of Truvada or Viread for use as PrEP and determine how it will provide it. As of March 2017, PrEP is available in Australia, Canada, France, Israel, Kenya, Peru, South Africa, and the U.S. In the UK, the National Health Service, which had been expected to approve Truvada for use as PrEP, decided in March 2016 not to provide PrEP as part of its prevention services. Instead, the National Health Service announced in December 2016 that it will conduct a three-year trial of PrEP.
Gilead, the producer of Truvada, has applied for regulatory approval in several additional countries; these approvals are pending as of March 2017.
Several recent clinical trials have shown that taking Truvada as oral PrEP (one pill by mouth daily) can help prevent HIV. These studies were conducted among men who have sex with men (MSM) and transwomen (women who assigned male at birth) in the U.S. and Latin America, and among heterosexual women and men in several African countries. The effectiveness for Truvada as PrEP varied from 44 percent to 73 percent additional protection against HIV infection in these three studies (known as the iPrex, TDF2, and Partners studies). A study in Bangkok tested oral daily tenofovir (Viread) as PrEP among more than 2,400 HIV-negative women and men who inject drugs. It showed that oral daily tenofovir reduced the risk of getting HIV by almost half (50 percent).
Other studies, however, have found these drugs not to be effective in preventing HIV. The FemPrEP study, for example, was stopped early because it did not seem to help in preventing HIV transmission. FemPrEP was testing the effectiveness of oral daily Truvada in Kenyan, Tanzanian, and South African women at high risk for HIV. The VOICE study, which tested oral daily tenofovir, oral daily Truvada (tenofovir plus emtricitabine), and one-percent tenofovir vaginal gel among more than 5,000 women in South Africa, Zimbabwe, and Uganda, found all three methods ineffective in preventing HIV transmission.
The Partners Demonstration Project showed the near elimination of HIV transmission among over 1,000 serodifferent (serodiscordant) heterosexual couples in Kenya and Uganda. The project tested a combination of PrEP and treatment as prevention. The researchers offered PrEP as a "bridge" -- the uninfected partner took PrEP while the partner living with HIV took the first six months of antiretroviral treatment. This strategy presumably protects the HIV-negative partner with PrEP during the time it takes for the partner living with HIV to become virally suppressed.
The project was completed in December 2016 and results are forthcoming. However, preliminary results through July 2014 noted only one new infection; this represents a 96 percent reduction in infections. Importantly, this reduction in infections applies to all infections, including those from someone other than one's regular sexual partner.
For any drug or other HIV prevention tool to work, it has to be used; and research tells us that it has to be used correctly and consistently. This is true for condoms and is proving true for PrEP as well. In the studies mentioned above, the key element in PrEP's success was adherence, which means taking the drug when and how it is prescribed.
In the FemPreEP and VOICE studies, there were low levels of adherence; fewer than one in three women took the drug regularly. Additionally, many women in the FemPrEP study did not consider themselves at risk for HIV. The other studies that showed a benefit had much higher rates of adherence. In all studies, people who took Truvada or tenofovir daily as prescribed were significantly less likely to acquire HIV when exposed during sex or injection drug use. The CDC reports that, in people at high risk for HIV who take PrEP consistently, the risk of HIV infection can be reduced by 92 percent.
We do not yet fully understand all of the reasons why people -- especially women -- have low levels of adherence to oral PrEP. This makes it very important to do more research looking at what issues might affect women's interest in or ability to take a drug for HIV prevention.
It is also important for women to know about and take part in the future research that will look at the unanswered questions about Truvada as PrEP. For more information about understanding, finding, and participating in research studies, see our fact sheet on Clinical Trials.
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