Treatment as prevention: Experts in the UK agree it works

This article originally appeared in HIV Treatment Update, a newsletter published by NAM between 1992 and 2013.

Roger Pebody summarises the statement released in January that should now guide how our doctors talk to us about treatment as prevention.

In January 2013, the British HIV Association (BHIVA) and the Department of Health’s Expert Advisory Group on AIDS (EAGA) published a joint position statement on the use of HIV treatment by people with HIV to reduce the risk of transmission.1

For the first time, the document provides health professionals in the UK with a consensus statement, developed by experts in this country, which can be used to guide discussions with individuals.


clinical trial

A research study involving participants, usually to find out how well a new drug or treatment works in people and how safe it is.

observational study

A study design in which patients receive routine clinical care and researchers record the outcome. Observational studies can provide useful information but are considered less reliable than experimental studies such as randomised controlled trials. Some examples of observational studies are cohort studies and case-control studies.


A serodiscordant couple is one in which one partner has HIV and the other has not. Many people dislike this word as it implies disagreement or conflict. Alternative terms include mixed status, magnetic or serodifferent.

treatment as prevention (TasP)

A public health strategy involving the prompt provision of antiretroviral treatment in people with HIV in order to reduce their risk of transmitting the virus to others through sex.

Clinicians, epidemiologists, policy experts and people living with HIV contributed to the document.

The position statement affirms that successful HIV treatment is "as effective as consistent condom use" in reducing HIV transmission, while cautioning that regular screening for viral load rebound and sexually transmitted infections is required. The key points are outlined here.

As effective as condoms

The statement notes that there is now conclusive evidence from a randomised clinical trial (considered to provide a high standard of reliable evidence), to show that transmission of HIV through vaginal sex is significantly reduced when an HIV-positive person is taking effective antiretroviral therapy (ART). In the HPTN 052 trial,2 a large trial which published its results in 2011, early treatment reduced HIV transmission to an uninfected partner by 96%.

“The observed reduction in HIV transmission in a clinical trial setting demonstrates that successful ART use by the person who is HIV positive is as effective as consistent condom use in limiting viral transmission,” the statement says.

The document includes some explanatory notes, which point out that there has never been a randomised controlled trial of the efficacy of condom use, compared to non-use. For that reason, there are no figures that can be directly compared. However, meta-analyses of observational studies of serodiscordant couples who reported 100% condom use have found the strategy to be about 80% effective in reducing HIV infection.3

Necessary conditions

The document states that the transmission risk during vaginal intercourse will be “extremely low”, provided certain conditions are fulfilled. These are:

  • There are no sexually transmitted infections (STIs) in either partner. (The document clarifies requirements for STI screening, including following sexual relationships outside a primary partnership – see below.)
  • The person with HIV has had a sustained blood viral load below 50 copies/ml for more than six months, including the most recent test.
  • Viral load testing occurs every three to four months (i.e. more regularly than in standard clinical care).

In the document’s explanatory notes, it is explained that in HPTN 052 there was a single confirmed case of HIV transmission from a person on treatment. This individual had only recently begun ART and would not have met the UK position statement’s requirement for an undetectable viral load for at least six months.

The authors say that this justifies the use of the phrase “extremely low risk”. They clarify that this is not the same as “zero risk”. Moreover, with the data that are available, it is not possible to give accurate and meaningful figures for the risk of transmission during a single sexual act.

Screening for sexually transmitted infections

The document notes that a sexually transmitted infection (STI) can increase the HIV viral load of a person with HIV, especially in their semen or vaginal secretions. Also, an STI in an HIV-negative person can increase their susceptibility to HIV.

For these reasons, frequent STI screening is recommended for both partners – at least every three to six months. If there is sex with people outside the couple, both partners need to have another STI screen before having sex again in order to be sure that they do not have an STI.

If there is any possibility that either partner has an STI, condoms are recommended.

Anal intercourse

The published research was primarily done with heterosexual couples and is assumed to relate primarily to vaginal intercourse. Data are not available for anal intercourse, either between men, or between men and women. “However, it is expert opinion that an extremely low risk of transmission can also be anticipated for these practices, provided the same conditions stated above are met,” according to the statement.

Discussion with people with HIV

Healthcare professionals should discuss the impact of ART on sexual transmission with all people living with HIV. For people not currently on therapy, the possibility of starting treatment in order to reduce transmission risk should be discussed.

Limitations of ART

The position statement notes that no single prevention method can completely prevent HIV transmission. Moreover, antiretroviral treatment has no effect on other sexually transmitted infections, whereas condoms can prevent their spread.

You can see the full version of the Position statement on the use of antiretroviral therapy to reduce HIV transmission at (it’s free to download).

The original version of this article was published on on 23 January 2013:  

  1. British HIV Association (BHIVA) and Expert Advisory Group on AIDS (EAGA) Position statement on the use of antiretroviral therapy to reduce HIV transmission. 2013.
  2. Cohen M et al. Antiretroviral treatment to prevent the sexual transmission of HIV-1: results from the HPTN 052 multinational randomized controlled ART. 6th International AIDS Society Conference on HIV Pathogenesis, Treatment and Prevention, Rome, abstract MOAX0102, 2011.
  3. National Institute of Allergy and Infectious Diseases (NIAID) Scientific Evidence on Condom Effectiveness for Sexually Transmitted Disease (STD) Prevention. NIAID, 2001.