HIV Treatment As Prevention

Treatment as prevention is a term increasingly used to describe HIV prevention methods that use antiretroviral treatment to decrease the chance of HIV transmission.

Antiretroviral treatment is already being used to reduce the risk of HIV from being passed on to another person - for example from an HIV positive pregnant woman to her unborn baby. It is also used to prevent HIV infection from being established in someone who has recently been exposed to the virus - for example a healthcare worker who has received a needlestick injury.

Although HIV treatment can significantly reduce infectiousness if taken exactly as prescribed, it cannot eliminate the risk of transmission completely, as HIV is never completely eradicated from the blood.

back to top When is it appropriate to use HIV treatment as prevention?

Treatment as prevention initiatives should be assessed like other methods of HIV prevention: there needs to be evidence to suggest that it will be highly effective; the resources in place to carry out the programme; enough funding to support the programme; and a clearly identified target population. Finally, and perhaps most fundamentally, the rights of the individual need to take precedence. Antiretroviral treatment can cause serious side effects and can lead to drug resistance if not taken exactly as prescribed. Therefore an HIV positive person has the right to decide whether or not to take the treatment by weighing up the potential disadvantages and benefits for their own health.

back to top How is HIV treatment as prevention currently being used?

Antiretroviral drugs Antiretroviral drugs

Across the world HIV-positive pregnant women take antiretroviral drugs to reduce the chances of transmitting HIV to their baby. Without intervention there is a 20-45 percent chance that a baby born to an HIV-infected mother will become infected.1 However, treatment for the mother during pregnancy significantly reduces this risk. UNAIDS estimate that between 1996 and 2008, 200,000 new HIV infections have been averted through preventing mother-to-child transmission (PMTCT) initiatives, which include the provision of prophylactic ARVs.2

In some countries if a person has been exposed to HIV they are offered a short course of antiretroviral drugs to reduce their chances of becoming infected with the virus. This is called post exposure prophylaxis, or PEP, and is used in both occupational and non-occupational settings. Health care workers are offered the treatment if they have received a needlestick injury or have been exposed to HIV through their work. There is no conclusive evidence to show that PEP works, but a combination of studies have suggested that it may be effective in reducing the risk of HIV infection.3 4 5

One idea of treatment as prevention that is currently being researched is pre-exposure prophylaxis (PrEP). PrEP involves providing people who are not infected with HIV with antiretroviral drugs before possible exposure to the virus, to stop them from becoming infected.

back to top What about the idea of HIV treatment as prevention for tackling the global AIDS epidemic?

In 2008 a group of Swiss scientists produced the first ever consensus statement which asserted that an HIV positive person who is taking effective antiretroviral therapy, has an undetectable viral load and is free from STDs, has a negligible risk of infecting others with the virus.6 Their conclusion was drawn from the results of studies which showed that if an effective treatment regimen is followed, one partner living with HIV will not pass on the virus to their HIV-negative partner. (For more information on this issue read AVERT's HIV transmission and antiretroviral therapy briefing sheet).

Since the Swiss statement, various studies have emerged that have investigated the relationship between viral load and HIV transmission. For example:

  • Observational studies looking at the effect of HIV treatment at the community level have found that as the number of people taking more effective HIV treatment has risen, community viral load has decreased, resulting in a reduction of new HIV infections.7 8 9
  • A large, randomised, placebo-controlled trial involving 3381 heterosexual African couples found antiretroviral therapy use by the HIV infected partner was associated with a 92 percent reduction in risk of HIV-1 transmission to their fellow partner.10
  • In May 2011, a study involving 1,763 HIV-serodiscordant couples was stopped before its original closing date of 2015.11 12 Interim analysis of the results showed those who started antiretroviral therapy immediately significantly lowered the risk of HIV transmission to their sexual partners, compared to those starting treatment later, when their CD4 count had fallen below 250 cells/mm3. The results showed a 96 percent reduction in risk of transmission, which was enough to release the results early and close the trial.

Taking into account the ‘Swiss statement’ and these other studies, some advocates have argued that a way to reduce the global AIDS epidemic would be to test everyone in 'high risk' groups and areas of generalised epidemics, and then immediately treat all of those diagnosed positive, regardless of whether their immune system is damaged.13 This 'test and treat' strategy is due to be tested in a large scale trial in KwaZulu-Natal, one of South Africa's provinces most affected by HIV and AIDS. The Treatment as Prevention (TasP) trial is expected to start in 2011 and is hoped to last until 2015.14

In 2011, a group of more than twenty HIV organisations from around the world, as well as hundreds of individuals, signed a declaration calling for country governments, multilateral organisations, and civil society to begin to use the evidence from the HPTN 052 trial to actively work towards early access to HIV treatment.15 The declaration also called for countries and donor programs to collect and monitor data in order the assess the feasibility and cost-effectiveness of increasing the treatment initiation threshold for people living with HIV to above 350 cells mm3, (the current WHO recommendation) and above 500 cells mm3.

Would the 'test and treat' strategy work?

When a person becomes infected with HIV it can take up to three months before the virus is detected by standard antibody tests. If a person is tested during this time they may receive a ‘false negative’ result, which means that even though the test is negative, they are in fact infected with HIV. It is also during this period of time when they are most infectious.

Therefore even if everyone who tested positive for HIV was treated with antiretroviral therapy, there would still be a group of people who had received a false negative result and who could still transmit the virus to others.

What would be the effects on the individual?

Once a person starts taking antiretroviral treatment, they have to take it exactly as prescribed, and for the rest of their life. If not, they significantly increase the risk of drug resistance. In addition, antiretroviral drugs often have unpleasant side effects and the long-term effects of taking the drugs are still unknown. These are some of the reasons why treatment is currently only recommended when HIV has attacked the immune system to an extent where, without treatment, the person's health will start to deteriorate.16 For many people living with HIV this means not starting treatment for years. Starting treatment at an earlier stage could therefore potentially be detrimental to the individual's health. It could also be viewed as unethical in countries where medical codes of practice make the care of the individual patient the doctor's first concern.

Is it feasible?

It is questionable whether the 'test and treat' strategy would work when people across the world do not have universal access to HIV testing, treatment and care.

HIV testing: It is not possible to detect all HIV infections even in well-resourced countries, when stigma, criminalisation and human rights abuses act as strong deterrents to accessing testing services. In the United States of America, for example, around one in five people living with HIV are unaware of their infection,17 and many people are still only tested once they have been diagnosed with an opportunistic infection. Barriers that prevent people from getting tested would therefore need to be addressed.

HIV treatment: Some countries are already struggling to supply treatment for those who really need it. In 2010, 47 percent of people living with HIV in low- and middle-income countries had access to treatment.18 This was up from the 36 percent of 2009, but still far short of the 2010 universal access target.19 If targets cannot be reached now, it is highly unlikely there would be enough funding to treat those whose HIV infection has not yet significantly damaged their immune system.

HIV care: Care is needed to ensure people living with HIV receive and adhere to effective antiretroviral therapy, to keep viral load to a minimum. In one review of access to HIV services in the USA, poor engagement in care was cited as a significant challenge to the idea of a 'test and treat' strategy for HIV prevention.20

Other costs: The 'test and treat' mathematical model proposed by Granich and colleagues21 has been criticised for substantially underestimating the actual costs that it would entail.22 In addition to the cost of providing more antiretroviral drugs, there would be administrative and human resources obstacles. These include finding additional doctors and nurses to prescribe the drugs, extra counsellors for pre and post-test counselling, and staff to support and encourage adherence among those taking treatment. It would be extremely difficult for countries to find the money for these costs in addition to finding the money to provide universal treatment. However, it has been argued that although in the short term the 'test and treat' strategy would be very costly, it has the potential to be cost-effective in the long term.23

back to top Is there a future for treatment as prevention?

Using HIV treatment as prevention to tackle the global AIDS epidemic does have some advantages; it would significantly increase the number of people who are aware of their HIV status, and millions of people worldwide who are in immediate need of HIV treatment would receive it. However, for treatment as prevention to work on this level, each case needs to be assessed on its own merit. The rights of the individual to choose whether to be treated before they need to be treated, would have to be paramount.

Treatment as prevention already works (in the case of PMTCT and PEP), but only because the individual is the first consideration and the programmes are part of a comprehensive, holistic prevention strategy. Treatment as prevention on a public health level needs to be complemented with education, condom use and behaviour change - other prevention strategies that have in many cases been largely successful.24 As the Joint United Nations Programme on HIV/AIDS state:

"UNAIDS strongly recommend a comprehensive approach to HIV prevention that plans and delivers an evidence informed and human rights based combination of programmes and policies, tailored to meet the needs of those most at risk, and including practical programmes to reduce underlying causes of vulnerability, such as gender inequality and HIV related stigma and discrimination... Antiretroviral therapy will play several roles in combination prevention strategies, along with other key strategies."25

References back to top

  1. De Cock et al (2000, March) 'Prevention of mother-to-child HIV transmission in resource-poor countries: translating research into policy and practice', JAMA 283(9)
  2. UNAIDS (2009) 'Report on the global AIDS epidemic'
  3. Cardo, D.M et al (1997) 'A case-control study of HIV seroconversion in health care workers after percutaneous exposure', The New England Journal of Medicine, November 20, 1997: (21)337:1485-1490
  4. Smith, D.K et al (2005) 'Antiretroviral post exposure prophylaxis after sexual, injection-drug use, or other nonoccupational exposure to HIV in the United States', MMWR, January 21, 2005 (54)1-20
  5. BASHH (2006, February) 'UK guidelines for the use of post-exposure prophylaxis for HIV following sexual exposure', International Journal of STD & AIDS, 17:81-92
  6. Vernazza, P et al (2008) 'Les personnes séropositives ne souffrant d'aucune autre MST et suivant un traitement antirétroviral efficace ne transmettent pas le VIH par voie sexuelle' Bulletin des médecins suisses 89 (5)
  7. Das-Douglas, M et al (2010) 'Decreases in community viral load are associated with a reduction in new HIV diagnoses in San Francisco', Session 10-Oral Abstacts, Paper #33, 17th Conference on Retroviruses and Opportunistic Infections
  8. Lima, V.D et al (2008) 'Expanded access to highly active antiretroviral therapy: A potentially powerful strategy to curb the growth of the HIV epidemic', The Journal of Infectious Diseases, 198:59-67
  9. WHO/UNAIDS/UNICEF (2011) ‚'Global HIV/AIDS Response: Epidemic update and health sector progress towards Universal Access 2011'
  10. Donnell, D et al (2010, 27th May) 'Heterosexual HIV-1 transmission after initiation of antiretroviral therapy: a prospective cohort analysis', The Lancet, DOI:10.1016/S0140-6736(10)60705-2
  11. HPTN (2011, 12th May) 'Initiation of antiretroviral treatment protects uninfected sexual partners from HIV infection (HPTN study 052' Press release [PDF]
  12. BBC News (2011, 12th May) 'Anti-retroviral drugs 'help reduce' HIV transmission'
  13. Granich, R.M et al (2009) 'Universal voluntary HIV testing with immediate antiretroviral therapy as a strategy for elimination of HIV transmission: a mathematical model', The Lancet, 2009; 373: 48-57.
  14. Africa Centre, ANRS & University of KwaZulu-Natal (2010, 29th November) Press release: 'What would be the impact of universal Test and Treat on the HIV pandemic?' [PDF]
  15. AVAC (2011, June 7th) 'We CAN End the AIDS Epidemic'
  16. WHO (2009, 30th November) 'Rapid advice: antiretroviral therapy for HIV infection in adults and adolescents'
  17. CDC (2010, July) 'HIV in the United States'
  18. WHO/UNAIDS/UNICEF (2011) ‚'Global HIV/AIDS Response: Epidemic update and health sector progress towards Universal Access 2011'
  19. WHO/UNAIDS/UNICEF (2010), 'Towards Universal Access: Scaling up priority HIV/AIDS Interventions in the Health Sector
  20. Gardner, E.M et al (2011) 'The spectrum of engagement in HIV care and its relevance to test-and-treat strategies for prevention of HIV infection', Clinical Infectious Diseases, 2011;52(6)793-800
  21. Granich, R.M et al (2009) 'Universal voluntary HIV testing with immediate antiretroviral therapy as a strategy for elimination of HIV transmission: a mathematical model', The Lancet, 2009; 373: 48-57.
  22. Wagner, B & Blower, S (2010, 18th September) 'Cost of eliminating HIV in South Africa have been underestimated', The Lancet, 376:953
  23. Johnston, K.M et al (2010) 'Expanding access to HAART: a cost-effective approach for treating and preventing HIV', AIDS 2010, Jul 31;24(12):1929-35
  24. Venkatesh, KA. et al (2011, October) 'Is expanded HIV treatment preventing new infections? Impact of antiretroviral therapy on sexual risk behaviors in the developing world' AIDS 25(16)
  25. UNAIDS (2009, 6th November) 'Antiretroviral treatment for prevention'