Introduction to HIV prevention

How can HIV transmission be prevented?

HIV can be transmitted in three main ways:

Sexual transmission
Transmission through blood
Mother-to-child transmission

For each route of transmission there are things that an individual can do to reduce or eliminate risk. There are also interventions that have been proven to work at the community, local and national level.¹
Wherever there is HIV, all three routes of transmission will take place. However the number of infections resulting from each route will vary greatly between countries and population groups. The share of resources allocated to each area should reflect the nature of the local epidemic - for example, if most infections occur among men who have sex with men then this group should be a primary target for prevention efforts.

"Knowing your epidemic in a particular region or country is the first, essential step in identifying, selecting and funding the most appropriate and effective HIV prevention measures for that country or region." - UNAIDS guidelines for HIV prevention ²

HIV prevention should be comprehensive, making use of all approaches known to be effective rather than just implementing one or a few select actions in isolation. Successful HIV prevention programmes not only give information, but also build skills and provide access to essential commodities such as condoms or sterile injecting equipment. It should be remembered that many people don’t fit into only one “risk category”. For example, injecting drug users need access to condoms and safer sex counselling as well as support to reduce the risk of transmission through blood.

Who needs HIV prevention?

Anyone can become infected with HIV, and so promoting widespread awareness of HIV through basic HIV and AIDS education is vital for preventing all forms of HIV transmission. Specific programmes can target key groups who have been particularly affected by a country’s epidemic, for example children, women, men who have sex with men, injecting drug users and sex workers. Older people are also a group who require prevention measures, as in some countries an increasing number of new infections are occurring among those aged over 50.³
HIV prevention needs to reach both people who are at risk of HIV infection and those who are already infected:

People who do not have HIV need interventions that will enable them to protect themselves from becoming infected.
People who are already living with HIV need knowledge and support to protect their own health and to ensure that they don’t transmit HIV to others - known as “positive prevention”. Positive prevention has become increasingly important as improvements in treatment have led to a rise in the number of people living with HIV.⁴ ⁵ ⁶

HIV counselling and testing are fundamental for HIV prevention. People living with HIV are less likely to transmit the virus to others if they know they are infected and if they have received counselling about safer behaviour. For example, a pregnant woman who has HIV will not be able to benefit from interventions to protect her child unless her infection is diagnosed. Those who discover they are not infected can also benefit, by receiving counselling on how to remain uninfected.⁷ ⁸ ⁹
The availability and accessibility of antiretroviral treatment is crucial; it enables people living with HIV to enjoy longer, healthier lives, and as such acts as an incentive for HIV testing. Continued contact with health care workers also provides further opportunities for prevention messages and interventions. Studies suggest that HIV-positive people may be less likely to engage in risky behaviour if they are enrolled in treatment programmes.¹⁰ ¹¹

Sexual transmission

What works?

Someone can eliminate or reduce their risk of becoming infected with HIV during sex by choosing to:

Abstain from sex or delay first sex
Be faithful to one partner or have fewer partners
Condomise, which means using male or female condoms consistently and correctly

There are a number of effective ways to encourage people to adopt safer sexual behaviour, including media campaigns, social marketing, peer education and small group counselling. These activities should be carefully tailored to the needs and circumstances of the people they intend to help.¹² ¹³ ¹⁴
Comprehensive sex education for young people is an essential part of HIV prevention. This should include training in life skills such as negotiating healthy sexual relationships, as well as accurate and explicit information about how to practise safer sex. Studies have shown that this kind of comprehensive sex education is more effective at preventing sexually transmitted infections than education that focuses solely on teaching abstinence until marriage.¹⁵ ¹⁶

A condom vending machine in Vatican City

Numerous studies have shown that condoms, if used consistently and correctly, are highly effective at preventing HIV infection.¹⁷ Also there is no evidence that promoting condoms leads to increased sexual activity among young people. Therefore condoms should be made readily and consistently available to all those who need them.¹⁸
There is now very strong evidence that male circumcision reduces the risk of HIV transmission from women to men by around 50%, which is enough to justify its promotion as an HIV prevention measure in some high-prevalence areas.¹⁹ However, studies of circumcision and HIV suggest that the procedure does not reduce the likelihood of male-to-female transmission, and the effect on male-to-male transmission is unknown.²⁰
Some sexually transmitted infections - most notably genital herpes - have been found to facilitate HIV transmission during sex. Treating these other infections may therefore contribute to HIV prevention.²¹ ²² Trials in which HIV-negative people were given daily treatment to suppress genital herpes have found no reduction in the rate at which they become infected with HIV. Nevertheless, there is evidence to suggest that treating genital herpes in HIV positive people may reduce the risk of them transmitting HIV to their partners. Further research is ongoing.²³

What are the obstacles?

It is usually not easy for people to sustain changes in sexual behaviour. In particular, young people often have difficulty remaining abstinent, and women in male-dominated societies are frequently unable to negotiate condom use, let alone abstinence. Many couples are compelled to have unprotected sex in order to have children. Others associate condoms with promiscuity or lack of trust.²⁴
Some societies find it difficult to discuss sex openly, and some authorities restrict what subjects can be discussed in the classroom, or in public information campaigns, for moral or religious reasons. Particularly contentious issues include premarital sex, condom use and homosexuality, the last of which is illegal or taboo in much of the world. Marginalisation of groups at high risk - such as sex workers and men who have sex with men - can be a major hindrance to HIV prevention efforts; authorities are often unwilling to allocate adequate resources to programmes targeting these groups.
Safe male circumcision demands considerable medical resources and some cultures are strongly opposed to the procedure.
Find out more about preventing sexual transmission of HIV.

Transmission through blood

What works?

People who share equipment to inject recreational drugs risk becoming infected with HIV from other drug users who have HIV. Methadone maintenance and other drug treatment programmes are effective ways to help people eliminate this risk by giving up injected drugs altogether. However, there will always be some injecting drug users who are unwilling or unable to end their habit, and these people should be encouraged to minimise the risk of infection by not sharing equipment.²⁵

Used syringes collected by a needle exchange in Puerto Rico

Needle exchange programmes have been shown to reduce the number of new HIV infections without encouraging drug use. These programmes distribute clean needles and safely dispose of used ones, and also offer related services such as referrals to drug treatment centres and HIV counselling and testing. Needle exchanges are a necessary part of HIV prevention in any community that contains injecting drug users.²⁶
Also important for injecting drug users are community outreach, small group counselling and other activities that encourage safer behaviour and access to available prevention options.²⁷
Transfusion of infected blood or blood products is the most efficient of all ways to transmit HIV. However, the chances of this happening can be greatly reduced by screening all blood supplies for the virus, and by heat-treating blood products where possible. In addition, because screening is not quite 100% accurate, it is sensible to place some restrictions on who is eligible to donate, provided that these are justified by epidemiological evidence, and don’t unnecessarily limit supply or fuel prejudice. Reducing the number of unnecessary transfusions also helps to minimise risk.²⁸ ²⁹
The safety of medical procedures and other activities that involve contact with blood, such as tattooing and circumcision, can be improved by routinely sterilising equipment. An even better option is to dispose of equipment after each use, and this is highly recommended if at all possible.
Health care workers themselves run a risk of HIV infection through contact with infected blood. The most effective way for staff to limit this risk is to practise universal precautions, which means acting as though every patient is potentially infected. Universal precautions include washing hands and using protective barriers for direct contact with blood and other body fluids.³⁰

What are the obstacles?

Despite the evidence that they do not encourage drug use, some authorities still refuse to support needle exchanges and other programmes to help injecting drug users. Restrictions on pharmacies selling syringes without prescriptions, and on possession of drug paraphernalia, can also hamper HIV prevention programmes by making it harder for drug users to avoid sharing equipment.
Many resource-poor countries lack facilities for rigorously screening blood supplies.³¹ In addition a lot of countries have difficulty recruiting enough donors, and so have to resort to importing blood or paying their citizens to donate, which is not the best way to ensure safety.
In much of the world the safety of medical procedures in general is compromised by lack of resources, and this may put both patients and staff at greater risk of HIV infection.
Find out more about preventing HIV transmission through blood

Mother-to-child transmission

What works?

HIV can be transmitted from a mother to her baby during pregnancy, labour and delivery, and later through breastfeeding. The first step towards reducing the number of babies infected in this way is to prevent HIV infection in women, and to prevent unwanted pregnancies.
There are a number of things that can be done to help a pregnant woman with HIV to avoid passing her infection to her child. A course of antiretroviral drugs given to her during pregnancy and labour as well as to her newborn baby can greatly reduce the chances of the child becoming infected. Although the most effective treatment involves a combination of drugs taken over a long period, even a single dose of treatment can cut the transmission rate by half.³²
A caesarean section is an operation to deliver a baby through its mother’s abdominal wall, which reduces the baby’s exposure to its mother’s body fluids. This procedure lowers the risk of HIV transmission, but is likely to be recommended only if the mother has a high level of HIV in her blood, and if the benefit to her baby outweighs the risk of the intervention.³³ ³⁴
Weighing risks against benefits is also critical when selecting the best feeding option. The World Health Organisation advises mothers with HIV not to breastfeed whenever the use of replacements is acceptable, feasible, affordable, sustainable and safe. However, if safe water is not available then the risk of life-threatening conditions from replacement feeding may be greater than the risk from breastfeeding. An HIV positive mother should be counselled on the risks and benefits of different infant feeding options and should be helped to select the most suitable option for her situation.³⁵

What are the obstacles?

In much of the world a lack of drugs and medical facilities limits what can be done to prevent mother-to-child transmission of HIV. Antiretroviral drugs are not widely available in many resource-poor countries, caesarean section is often impractical, and many women lack the resources needed to avoid breastfeeding their babies.
HIV-related stigma is another obstacle to preventing mother-to-child transmission. Some women are afraid to attend clinics that distribute antiretroviral drugs, or to feed their babies formula, in case by doing so they reveal their HIV status.
Find out more about preventing mother-to-child transmission (PMTCT) and why PMTCT programmes are failing to reach most women in need.

Policy measures

To be successful, a comprehensive HIV prevention programme needs strong political leadership. This means politicians and leaders in all sectors must speak out openly about AIDS and not shy away from difficult issues like sex, sexuality and drug use.
An effective response requires strategic planning based on good quality science and surveillance, as well as consideration of local society and culture. All sectors of the population should be actively involved in the response, including employers, religious groups, non-governmental organisations and HIV-positive people. Many of the world's most successful HIV prevention efforts have been led by the affected communities themselves.
HIV epidemics thrive on stigma and discrimination related to people living with the virus and to marginalised groups such as sex workers. Their spread is also fueled by gender inequality, which restricts what women can do to protect themselves from infection. Protecting and promoting human rights should be an essential part of any comprehensive HIV prevention strategy. This includes legislating against the many forms of stigma and discrimination that increase vulnerability.

References

Mayer K. & Pizer H. (eds) (2009), 'HIV Prevention: A Comprehensive Approach'.
UNAIDS (2007), 'Practical Guidelines for Intensifying HIV Prevention'.
CDC (2007) 'HIV/AIDS surveillance report: Cases of HIV infection and AIDS in the United States and Dependent Areas, 2007'.
GNP+ (2009, April), 'Living 2008: The Positive Leadership Summit Report'.
Kalichman S. (ed) (2006), 'Positive Prevention: Reducing HIV Transmission Among People Living with HIV/AIDS' Springer.
International HIV/AIDS Alliance, "Positive Prevention: Prevention Strategies for People with HIV/AIDS", July 2003
Richardson et al, "Effect of brief safer-sex counseling by medical providers to HIV-1 seropositive patients: a multi-clinic assessment", AIDS 18(8), May 2004
Voluntary HIV-1 Counseling and Testing Efficacy Study Group, "Efficacy of voluntary HIV-1 counselling and testing in individuals and couples in Kenya, Tanzania, and Trinidad: a randomised trial", The Lancet 356(9224), July 2000
UNAIDS, "The impact of Voluntary Counselling and Testing", 2001
Kennedy et al, "The impact of HIV treatment on risk behaviour in developing countries: A systematic review", AIDS Care 19(6), July 2007
Crepaz et al, "Highly active antiretroviral therapy and sexual risk behavior: a meta-analytic review", JAMA 292(2), 14 July 2004
Lamptey and Price, "Social marketing sexually transmitted disease and HIV prevention: a consumer-centered approach to achieving behaviour change", AIDS 12 Suppl 2, 1998
Peersman and Levy, "Focus and effectiveness of HIV-prevention efforts for young people", AIDS 12 Suppl A, 1998
UNAIDS, "Sexual behavioural change for HIV: Where have theories taken us?", 1999
Santelli et al, "Abstinence and abstinence-only education: a review of U.S. policies and programs", J Adolesc Health 38(1), January 2006
See AVERT.org's abstinence page
See AVERT.org's condoms page
UNAIDS, "HIV Prevention Fact sheet", 2004
NIAID, "QUESTIONS AND ANSWERS: NIAID-Sponsored Adult Male Circumcision Trials in Kenya and Uganda", 13 December 2006
Aidsmap, "Circumcising HIV positive men may increase HIV infections in female partners, but fewer STIs seen", 3 February 2008
WHO, "Treatment for sexually transmitted infections has a role in HIV prevention", 16 August 2006
Hitchcock and Fransen, "Preventing HIV-1: lessons from Mwanza and Rakai", The Lancet 353(9152), February 1999
Celum et al, "Effect of aciclovir on HIV-1 acquisition in herpes simplex virus 2 seropositive women and men who have sex with men: a randomised, double-blind, placebo-controlled trial", The Lancet 371(9630), 21 June 2008
Marston and King, "Factors that shape young people's sexual behaviour: a systematic review", Lancet 368(9547), 4 November 2006
WHO, "Effectiveness of Drug Dependence Treatment in Preventing HIV Among Injecting Drug Users", March 2005
WHO, "Effectiveness of Sterile Needle and Syringe Programming in Reducing HIV/AIDS Among Injecting Drug Users", January 2005
WHO, "Effectiveness of Community-based Outreach in Preventing HIV/AIDS Among Injecting Drug Users", April 2004
UNAIDS, "Blood safety and HIV", 1997
WHO, "Aide-Memoire for National Blood Programmes", July 2002
WHO, "Universal Precautions, Including Injection Safety"
Takei T et al (2009), 'Progress in Global Blood Safety for HIV' Journal of Acquired Immune Deficiency Syndromes 52.
See AVERT.org's pregnancy page
The European Mode of Delivery Collaboration, "Elective caesarean-section versus vaginal delivery in prevention of vertical HIV-1 transmission: a randomised clinical trial", The Lancet 353(9165), March 1999
The International Perinatal HIV Group, "The mode of delivery and the risk of vertical transmission of human immunodeficiency virus type 1--a meta-analysis of 15 prospective cohort studies", NEJM 340(13), April 1999
WHO/UNICEF/UNAIDS/UNFPA, "HIV and infant feeding: Guidelines for decision makers", 2003

AIDS - HIV