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Does HIV prevention work?

Given the large sums that are spent on interventions to reduce the spread of HIV, it is right that their effectiveness and efficiency should be carefully assessed. There is now a growing body of evidence analysing what works in HIV prevention, and suggesting the best ways of evaluating prevention programmes. This feature summarizes the key points, with plenty of links to more detailed on-line documentation.

Assessing what works

It is increasingly common for HIV prevention efforts to be subject to stringent evaluation of their impact. While it is relatively easy to measure a project's outputs, such as the number of condoms or needles distributed, or the number of individuals contacted through an outreach scheme, it is less easy to measure a project's outcomes in terms of individual behaviour change or reduction in the number of new HIV infections.

The Center for AIDS Prevention Studies (CAPS) has developed a guide to evaluating behaviour change efforts, which includes case-studies of research techniques, example questions and advice on preparing evaluation proposals. A detailed report on Evaluating HIV/AIDS Prevention Programs in Community-Based Organizations, published by the US National AIDS Fund, is also available online.

A broader overview of good practice in planning, implementing and evaluating HIV and STD prevention interventions has been published by the US Centers for Disease Control and Prevention (CDC). The CDC has also published the results from its AIDS Community Demonstration Projects (ACDPs) -- experimental, community-level HIV prevention programs targeting high-risk populations in five U.S. cities.

What works in HIV prevention?

The Institute for Health Policy Studies has published a useful table contrasting what works in HIV prevention versus what does not work. Characteristics of effective programs include:

Another detailed review of what works in HIV prevention was published by the Center for Behavioral Research and Services in 1996. A further in-depth evaluation was commissioned by the US Department of Health and Human Services, and published in 1996. CAPS have also published a short factsheet summarizing effective methods of HIV prevention.

Effective interventions for specific groups

In many countries, most new infections are linked to injecting drug use. For instance, according to CAPS, "the majority of the estimated 41,000 annual new HIV infections in the US are occurring among injection drug users (IDUs), their sexual partners, and their offspring". In addition to community outreach and on-demand drug treatment programs, needle exchanges and other means of access to clean injecting equipment have been demonstrated to be effective. As summarized in a CAPS factsheet, needle exchanges in New York City and New Haven have been associated with reduced rates of HIV transmission, and there is further evidence of benefit in terms of reduced rates of hepatitis B and C. A more detailed account is contained in a 1993 evaluation of needle exchange programs prepared by the University of California for the CDC. The responses of the CDC and Clinton administration health agencies to the report are also available online.

Condoms are undoubtedly an effective means of reducing sexual HIV transmission -- despite the scare-stories to the contrary put about by the religious right. Promoting correct and consistent condom use, and tackling obstacles such as embarrassment, negotiation with sexual partners, insufficient knowledge or physical practical dislike of condoms are important components of campaigns to reduce sexual transmission.

Among gay men, prevention approaches that have been shown to be effective include small group counseling and skills training, peer outreach, and community interventions. CAPS has also published a factsheet looking at the prevention needs of young gay men in particular, and analysing the (relatively few) programs that have been thoroughly evaluated. For an activist perspective on how the early successes of gay activism in responding to HIV have been excluded from official histories, see Peter Scott's article White Noise.

Schools-based sex education programs were evaluated by the US Department of Health and Human Services in 1994. Their report concluded that sex education does not increase or hasten sexual activity, at least among older students, and in some cases can increase the use of condoms and contraceptives. Effective programs had the following common characteristics:

(a) theoretical grounding in social learning or social influence theories, (b) a narrow focus on reducing specific sexual risk-taking behaviors, (c) experiential activities to convey the information on the risks of unprotected sex and how to avoid those risks and to personalize that information, (d) instruction on social influences and pressures, (e) reinforcement of individual values and group norms against unprotected sex that are age and experience appropriate, and activities to increase relevant skills and confidence in those skills.

Obstacles to effective prevention

As CAPS has outlined, good HIV prevention interventions are not only effective at preventing new infections; they are also cost-effective uses of public funds. One million dollars spent on HIV prevention in a high prevalence population can save $2.7 million in medical and economic costs.

However, knowing what works is useless if that knowledge is not acted upon. CAPS has outlined a series of obstacles that obstruct effective HIV prevention, including US federal opposition to needle exchanges, laws that restrict sex education and the failure to target prevention funds towards the groups at greatest risk.