Truvada, the HIV prevention medication you’ve likely never heard of, was approved for use by the FDA for “pre-exposure prophylaxis” (PrEP) in July, 2012. The drug performed well against placebos in preventing HIV infection, but concerns remained about its performance in the real world.

HIV is a serious problem today; reports suggest that over a million Americans are infected with the disease every year, and that 13% remain unaware of their infection. Most at risk are gay and bisexual men, who suffer the highest rates of HIV infection according to the CDC.

Now, according to a report from Reuters, two studies have borne out the new HIV pill’s effectiveness in a real-world setting.

The first study, conducted in San Francisco and published in Clinical Infectious Diseases, followed 657 people. Most of the subjects were gay and bisexual men between 20-68 years of age who were part of the Kaiser Permanente healthcare system, a health consortium in California. The study followed its subjects for three years, all of whom took the Truvada HIV pill daily.

Of those 657 people, no new cases of HIV were found over the three year study. Half of the participants did contract different STIs (Sexually-Transmitted Infections) during the period of study, indicating that they were still participating in high-risk sexual activity; they simply did not contract HIV from those activities while taking Truvada. 41% also reported a reduced use of condoms, although the lead author of the study, Dr. Jonathan Volk, was careful to note that there may be other reasonable explanations for this finding, including the subjects’ entering new monogamous relationships.

That said, Volk concluded that without the pill, “we would have seen some new HIV infections.”

A second study of Truvada, performed in the UK and published in The Lancet, concluded that gay men who began Truvada PrEP suffered significantly fewer new infections than men who had to wait a year for access to the HIV pill.

For those taking Truvada, there was an HIV infection rate of one to two new infections per hundred men. For those not on Truvada, the HIV infection rate was nine in every hundred.

“When you do the math, the reduction was an 86 percent decrease,” said Dr. Kenneth Mayer of The Fenway Institute in Boston. Dr. Mayer also wrote an editorial accompanying the study, noting that two-thirds of the men diagnosed with HIV during the study were likely already infected before they had started taking Truvada.

When the UK researchers reached their conclusions about Truvada’s effectiveness against HIV, they ended the study in order to administer the new anti-HIV pill to all participants.

Dr. Volk says that the next step is to get Truvada to other high-risk populations, such as transgender women.

“I don’t think PrEP is the magic bullet, but we know that it does work really well. It’s great to know we have options.”

[Photo Illustration by Justin Sullivan/Getty Images]