Antiretroviral medications (ARVs) are primarily used to increase the health and well-being of people living with the virus. The U.S. Department of Health and Human Services recommends ARV treatment for all people living with HIV, regardless of their CD4 cell count.

Treatment as prevention (TasP) refers to the use of antiretroviral (ARV) medication to prevent HIV transmission.

TasP involves prescribing ARVs to those who are living with HIV in order to reduce the amount of virus in their blood to undetectable levels so that there is effectively no risk of transmission of HIV. An undetectable viral load is defined as less than 200 copies/milliliter of HIV in the blood.

In 2011, the HIV Prevention Trials Network (HPTN 052) study demonstrated that the use of ARVs by HIV-positive heterosexual men and women cut the chance that their HIV-negative partner would become infected by roughly 96 percent. The final study results were announced in 2015 and found that no participant with a fully suppressed viral load transmitted the virus to his or her long-term HIV-negative partner.

In 2014, interim analysis of the ongoing PARTNER trial—which focuses on heterosexual and gay mixed-HIV-status couples in which the HIV-positive partner is taking ARVs—found that there were no transmissions of the virus within the couple when the partner with HIV remained undetectable (i.e., had a fully suppressed virus).

In 2017, the results of the Opposites Attract study, which included 343 gay couples where one partner had HIV and the other did not, found that there were zero cases of transmission of the virus in 16,889 acts of condomless anal sex.

Later that year, the Centers for Disease Control and Prevention noted, “Across three different studies, including thousands of couples and many thousand acts of sex without a condom or pre-exposure prophylaxis (PrEP), no HIV transmissions to an HIV-negative partner were observed when the HIV-positive person was virally suppressed.”

The fact that people living with HIV on effective treatment do not sexually transmit the virus is known as U=U, or undetectable equals untransmittable.

The success of TasP is dependent on people adhering to their HIV treatment.

While it is acknowledged that TasP alone will not end the global HIV epidemic, it is an essential part of the HIV prevention toolbox.

Other examples of treatment as prevention include:

Last Reviewed: July 28, 2020