A pill designed to prevent HIV is working even better than people thought

HIV preventative medicine is doing what it’s supposed to do, even for high-risk populations that aren’t using other forms of protection, according to new research from a health insurer.

HIV, which stands for human immunodeficiency virus, can lead to acquired immunodeficiency syndrome, or AIDS. Unlike some other viruses, which the body can get rid of over time, once you have HIV, you have it for life.

And 1.2 million Americans are estimated to have it. Yet new research finds that HIV may be able to be prevented in some people with a daily pill.

The pill, called Truvada, has been shown to reduce the risk of HIV infection in people who are at high risk by up to 92%. The CDC defines people at high, or “substantial risk” of contracting HIV as people who either a) have unprotected sex with people who may have HIV or b) have injected illicit intravenous drugs and shared needles.

In a study published Tuesday and conducted by San Francisco-based health insurer Kaiser Permanente, researchers found that of the 657 high-HIV-risk patients they studied who were taking Truvada (all of whom were HIV negative at the time the study began), none contracted the virus over an almost-three-year period, even if they contracted other sexually transmitted diseases during that time.

Since the study was not a clinical trial — the strongest way to test the effects of a treatment which involves giving the treatment to only half of patients while the others are given a placebo —  more research is likely needed. Even so, the results are promising, experts say.

What is Truvada?

Since its FDA approval in 2004, Truvada has been used to decrease the amount of HIV in the blood of people diagnosed with HIV, which helps control symptoms and reduce your chances of spreading the virus to others. HIV can still persist even when someone’s viral load is undetectable, however, in semen, vaginal and rectal fluids, breast milk, and other parts of the body.

In 2012, Truvada was also approved to reduce the risk of contracting the virus, which classified it as a prevention method called pre-exposure prophylaxis (PrEP). Since then, the CDC has recommended the pill for anyone classified as at high risk of contracting HIV. PrEP drugs, of which Truvada is currently the only one available, help keep the HIV virus from latching onto healthy cells. The drug has to be present for the body to resist the virus, which is why it has to be taken daily.

Truvada has some intense side effects — the most serious being harm to your bones and kidneys — which is why it’s recommended mainly for people who are HIV negative and are at high risk of contracting the virus.

What did they find?

For the study, researchers tracked 657 people taking Truvada daily from 2012 (after it was approved to reduce the risk of contracting the virus) to February 2015. They were screened for HIV every few months, and later answered surveys about their sexual behavior. Of the participants, 99% (653) were men who have sex with men between 20 and 68 years old.

While it wasn’t a clinical trial, the study still appears to have dispelled some major concerns, including that more people would develop HIV as a result of using condoms less frequently.

Of the 657 people involved in the study, more than half did contract a treatable STI, suggesting that condoms were in fact used less frequently. Regardless, the number of people who contracted HIV stayed zero.

Treating HIV

Truvada is part of a class of HIV medications that keep the virus from making copies of itself in an effort to keep the viral load almost undetectable. It’s often a part of the drug regimen for people who are just beginning to be treated for HIV. Around the late 1990s and early 2000s, a large number of effective drugs like Truvada became available to treat HIV and AIDS, almost 20 years after the disease was first discovered.

Since then, these kinds of drugs have done a good job of keeping the virus at bay, but there haven’t been any concrete steps taken toward a potential cure as there have been with other infectious diseases like hepatitis C.

But researchers are working to make the drugs that are available even better: Yesterday, Gilead announced successful results from its phase 3 trial of a new combination pill nicknamed F/TAF to treat HIV, which it’s calling the “next-generation backbone” for HIV treatment. The new medicine is similar to Truvada, but has better long-term safety.