What Is Treatment as Prevention?
Treatment as Prevention (TasP) refers to taking HIV medicine to prevent the sexual transmission of HIV. It is one of the most highly effective options for preventing HIV transmission.
People with HIV who take HIV medicine (called antiretroviral therapy or ART) as prescribed and get and keep an undetectable viral load—a very low level of HIV in the blood—can stay healthy and have effectively no risk of sexually transmitting HIV to their HIV-negative partners. This is sometimes called undetectable = untransmittable (U=U).
TasP works when a person with HIV takes HIV medicine exactly as prescribed and has regular follow-up care, including routine viral load tests to ensure their viral load stays undetectable.
Taking HIV Medicine to Stay Healthy and Prevent Transmission
HIV treatment involves taking highly effective medicine that reduces the amount of HIV in your body. HIV medicine is recommended for everyone with HIV, and people with HIV should start HIV medicine as soon as possible after diagnosis, even on that same day.
People on HIV treatment take a combination of HIV medicines (called an HIV treatment regimen). A person's initial HIV treatment regimen generally includes three HIV medicines from at least two different HIV drug classes that must be taken every day. Many people with HIV take two or more different HIV medicines combined in one pill. Long-acting injections of HIV medicine, given every two months, are also available if your health care provider determines that you meet certain requirements.
If taken as prescribed, HIV medicine reduces the amount of HIV in your blood (also called your viral load) to a very low level, which keeps your immune system working and prevents illness. This is called viral suppression, defined as 200 copies of HIV per milliliter of blood.
HIV medicine can also make your viral load so low that a standard lab test can’t detect it. This is called having an undetectable viral load. Almost everyone who takes HIV medicine as prescribed can achieve an undetectable viral load, usually within 6 months after starting treatment. Many will bring their viral load to an undetectable level very quickly, but it could take more time for a small portion of people just starting HIV medicine.
There are important health benefits to getting the viral load as low as possible. People with HIV who know their status, take HIV medicine as prescribed, and get and keep an undetectable viral load can live long and healthy lives.
There is also a major prevention benefit. People with HIV who take HIV medicine as prescribed and get and keep an undetectable viral load have effectively no risk of sexually transmitting HIV to their HIV-negative partners.
Keep Your Viral Load Undetectable
HIV treatment is not a cure and HIV is still in your body, even when your viral load is undetectable, so you need to keep taking your HIV medicine as prescribed. If you skip doses of your HIV medicine, even now and then, you give HIV the chance to multiply rapidly. This could weaken your immune system, and you could become sick.
If you have stopped taking your HIV medicine or are having trouble taking all the doses as prescribed, talk to your health care provider as soon as possible. Your provider can help you get back on track and discuss the best strategies to prevent transmitting HIV to your sexual partners until your viral load is confirmed to be undetectable again.
How Do We Know Treatment as Prevention Works?
Large research studies with newer HIV medicines have shown that treatment is prevention. Over several years, these studies monitored thousands of male-female and male-male couples in which one partner has HIV and the other does not. No HIV transmissions were observed when the HIV-positive partner was virally suppressed. This means that if you keep your viral load undetectable, there is effectively no risk of transmitting HIV to someone you have vaginal, anal, or oral sex with.
In addition to preventing sexual transmission of HIV, studies have shown that there are other prevention benefits of taking HIV medicine to get and keep an undetectable viral load:
- It reduces the risk of HIV transmission to the child during pregnancy, labor, and delivery. If a pregnant person takes HIV medicine daily as prescribed throughout pregnancy, labor, and delivery and gives HIV medicine to the infant for 4-6 weeks after giving birth, the risk of transmitting HIV to the baby can be 1% or less.
- It substantially reduces, but does not eliminate, the risk of transmitting HIV through breastfeeding. The current recommendation in the United States is that mothers with HIV should not breastfeed their infants.
- It may reduce HIV transmission risk for people who inject drugs. Scientists do not have enough data to know whether having a suppressed or undetectable viral load prevents HIV transmission through sharing needles, syringes, or other injection drug equipment (for example, cookers). It very likely reduces risk, but it’s unknown by how much. Even if you are taking HIV medicine and have an undetectable viral load, use new equipment each time you inject and do not share needles and syringes with other people.
Talk with Your Health Care Provider about Getting to Undetectable
Talk with your health care provider about the benefits of HIV treatment and which HIV medicine is right for you. Discuss how frequently you should get your viral load tested to make sure you get and keep an undetectable viral load. If your lab results show that the virus is detectable or if you are having trouble taking every dose of your medicine, you can still protect your HIV-negative partner by using other methods of preventing sexual transmission of HIV such as condoms, safer sex practices, and/or pre-exposure prophylaxis (PrEP) for an HIV-negative partner until your viral load is undetectable again. Talk to your partner about post-exposure prophylaxis (PEP) if you think they may have had a possible exposure to HIV (for example, if the condom breaks during sex and you don’t have an undetectable viral load).
Taking HIV medicine to maintain an undetectable viral load does not protect you or your partner from getting other sexually transmitted infections (STIs), so talk to your provider about ways to prevent other STIs.
Talk to Your Partner
TasP can be used alone or in conjunction with other prevention strategies. Talk about your HIV status with your sexual partners and decide together which prevention methods to use. Some states have laws that require you to tell your sexual partner that you have HIV in certain circumstances.