A Pill to Prevent HIV?

By: Alia Hoyt
Truvada (brand name for pre-exposure prophylaxis or  PrEP pills) sit on a tray. PrEP pills are shown to be effective at preventing HIV. Justin Sullivan/Getty Images
Truvada (brand name for pre-exposure prophylaxis or PrEP pills) sit on a tray. PrEP pills are shown to be effective at preventing HIV. Justin Sullivan/Getty Images

In the ongoing war against human immunodeficiency virus (HIV), enterprising scientists are winning yet another battle, thanks to the development of highly effective HIV prevention pills. Known in medical circles as pre-exposure prophylaxis (PrEP), the tablets are designed specifically to help high-risk groups avoid contracting the virus. In fact, when taken as directed (one pill per day, consistently) PrEP reduces infection risk in these groups by about 92 percent.

You probably already know that major strides have been made in the development and use of antiretroviral drugs to treat HIV, which causes acquired immune deficiency syndrome (AIDS). PrEP is actually a combination of two of the three drugs commonly used to treat HIV, although in lower doses. This is because it takes less muscle to prevent the virus from taking root than it does to treat an infection already in progress, according to Dawn K. Smith, M.D., biomedical interventions activity lead in the epidemiology branch of the division of HIV/AIDS prevention at the Centers for Disease Control and Prevention (CDC).


PrEP is not recommended for people who simply want to avoid HIV at all costs. Instead, it's for HIV-negative people who repeatedly engage in behaviors that expose them to HIV, such as intravenous drug use and unsafe sex with partners who may be HIV-positive. Bisexual or gay men who've had unprotected anal sex in the last six months, or who've been diagnosed with a different sexually transmitted disease (STD) also can be considered candidates for PrEP.

People in an ongoing relationship with a partner who is HIV-positive may also take PrEP, although it isn't always necessary. In fact, if treatment is effectively suppressing the viral load of the HIV-positive partner, infection risk is actually very low.

“It's not the case that all negative people who have positive partners may want to go on PrEP,” says Dr. Smith. “It's a situation where there may be exposure to the virus, particular people who have not yet started treatment, or are on treatment that has not yet suppressed their viral load.”

PrEP, which is also known by the commercial name Truvada, is still relatively new to the marketplace. Initial studies deeming it safe and effective for human use have been published in 2010, 2012 and 2014, and continue to be conducted.

Risks appear to be minimal, with side effects only occurring in about 10 percent of patients, and typically are limited to nausea, vomiting, headache and diarrhea during the first couple of weeks of treatment. “For most there really are no symptoms,” says Smith. “They say they really can't tell that they're taking a medication.”

Despite the positive feedback, a couple of challenges do face PrEP proponents. Although it is currently available and can be prescribed by any licensed medical provider, it's relatively new, so some physicians have not yet learned about PrEP as a viable option for HIV prevention.

“We have some homework to do in terms of making people who are at risk of HIV aware that they can do this to reduce risk,” Smith explains. “We also need to better educate providers about what it is, who it's indicated for and how they should go about prescribing it.”

PrEP has also inspired a debate regarding whether the drug will lead to a decline in condom use. Condoms also protect against STDs other than HIV, so the fear is that those incidence rates will start to climb again if PrEP use really takes off. Although long-term data is still in process, it's worth noting that at least one study reported that most PrEP users continued condom use, as well, and also experienced reduced negative emotions such as guilt, fear and stress.

Experts are strongly urging high-risk individuals to add PrEP to their HIV-prevention toolkit, rather than tossing other safety precautions by the wayside in favor of popping a daily pill. “PrEP plus condoms is more effective than either one alone,” says Smith. “Condoms protect against sexually transmitted infections, and clean injection equipment protects against hepatitis and other blood borne infections in addition to HIV.”

Ideally, the beneficial effects of PrEP will have worldwide reach, especially in low-resource countries where HIV/AIDS runs rampant. According to Dr. Smith, many affected developing countries, such as South Africa, already have access to PrEP in the form of HIV treatment drugs, so it's a matter of working with authorities to develop and implement prevention guidelines.