Pre-Exposure Prophylaxis (PrEP)
What is Pre-Exposure Prophylaxis (PrEP)?
Could the medications used to treat HIV infection also keep you from getting HIV in the first place? Scientists believe they may have evidence that the answer is “Yes.”
Using HIV drugs to prevent infection is called pre-exposure prophylaxis, or PrEP.
Taking medicine before exposure to an infectious agent is nothing new. Public health officials often advise travelers to take medications or be vaccinated before they visit areas where infectious diseases, such as malaria or typhoid, are common. Researchers believe that the same concept may work to protect you from HIV.
Currently, there are no official medical guidelines on using PrEP for HIV prevention, but researchers have promising evidence that shows PrEP’s effectiveness.
Results from two studies of pre-exposure prophylaxis, or PrEP, released in July 2011 (TDF2 study and the Partner’s PrEP study (PDF 144 KB)) provided clear evidence that the antiretroviral drugs used to treat HIV can be used to prevent heterosexual transmission of HIV from men to women and from women to men. This follows findings of the iPrEx study among men who have sex with men reported in November 2010 which found that a daily dose of an oral antiretroviral drug taken by HIV-negative study participants significantly reduced, but did not eliminate, the risk of acquiring HIV infection.
The next step is to determine how these scientific findings can be put to use in real world settings. The drugs involved in these studies are approved by the Food and Drug Administration (FDA) for HIV treatment, but are not currently FDA-approved for PrEP. In January 2011, CDC published interim guidance for physicians on HIV Pre-Exposure Prophylaxis for Men Who Have Sex with Men (PDF 623 KB) to help inform clinical practice as formal U.S. Public Health Service guidelines are being developed. At present, CDC urges heterosexual men and women and their health care providers in the United States to await that guidance before considering PrEP. However, if providers have patients for whom they believe the initiation of PrEP is urgent, CDC recommends following the cautions and procedures previously published for PrEP use in MSM.
Importantly, anyone considering using PrEP should know:
- PrEP should only be used among individuals who have been confirmed to be HIV-negative. Initial and regular HIV testing is critical for anyone considering using PrEP. All individuals considering PrEP must also be evaluated for other health conditions that may impact PrEP use.
- PrEP should never be seen as the first line of defense against HIV. It was only shown to be effective in clinical trials when provided in combination with regular HIV testing, condoms, and other proven prevention methods.
- Taking PrEP daily is critical. No other dosing regimen was evaluated in these studies.
- PrEP must be obtained and used in close collaboration with health care providers to ensure regular HIV testing, risk reduction and adherence counseling, and careful safety monitoring. Anyone considering using PrEP should speak with his or her doctor.
- PrEP has only been shown in clinical trials to reduce HIV infection among heterosexual men and women and among men who have sex with men. At this time, there are no data on its benefits or risks among injection drug users.
- Because pregnant and breastfeeding women were excluded from participation in PrEP trials, further evaluation of available data will be needed before any recommendations can be made regarding the use of PrEP for women during conception, pregnancy, or breastfeeding.
For more information, visit CDC’s PrEP page.
Fact Sheets & Print Materials
- CDC – Pre-Exposure Prophylaxis (PrEP) for HIV Prevention: Promoting Safe and Effective Use in the United States
- CDC – Q&A: CDC's Clinical Studies of Pre-Exposure Prophylaxis for HIV Prevention
- CDC – Fact Sheet: Trials of Pre-Exposure Prophylaxis for HIV Prevention
Related Topics on AIDS.gov
Frequently Asked Questions
If PrEP proves to be effective, why would I need to bother with risk-reduction strategies? Can’t I just take a pill and be safe?
You can still get HIV when taking PrEP. The most recent clinical trial of PrEP, iPrEx, found that PrEP is only partially effective. If approved for use as an HIV prevention strategy, it should be used with – not instead of – condoms, safer sex practices and other HIV prevention methods. So, if proven to be effective, PrEP could add another layer of protection. It’s also important to remember that many antiretroviral medications have significant side effects.
- AIDS.gov blog posts about PrEP
- NIH – Daily Dose of HIV Drug Reduces Risk of HIV Infection (11/23/10)
- NIH – iPrEx study results and Q&A (11/23/10)
- CDC PrEP Resources Page
- HIV Prevention Trials Network
Immediate Cautions for MSM Considering PrEP as an HIV Prevention Strategy (scroll down page)
Last revised: 07/25/2011