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Although a person with detectable HIV-1 RNA is generally considered to be infectious at all times, the degree of infectious potential may vary depending on the stage of the disease. Indeed, primary or acute HIV infection has been found to be associated with high rates of transmission due to high HIV-1 RNA levels during these periods. In one study, persons with HIV were shown to be 26 times more infectious during the primary infection period than during the asymptomatic period. This same study also showed that transmission rates in persons diagnosed with AIDS are increased due to high plasma HIV-1 RNA during this period of time.
Along with stage of HIV infection, the presence of STDs in individuals with HIV can facilitate HIV transmission by increasing genital shedding of HIV. Therefore, detection, treatment, and behavioral interventions to reduce the transmission of STDs are an important part of an HIV prevention strategy.
Sexual Risk Reduction Interventions
Although changing behavior associated with increased HIV risk during sexual activity (eg, having multiple sexual partners, failure to use a condom) decreases the risk of infection, limited data are available to demonstrate that a behavioral intervention targeting risk reduction can result in decreased HIV incidence. Project RESPECT was a study designed to assess the efficacy of risk-reduction counseling in 5 US public STD clinics between 1993 and 1996. In this study, 5758 heterosexual HIV-uninfected people were randomized to 1 of 3 arms:
Questionnaires were collected at 3, 6, 9, and 12 months, and STD tests were performed at 6 and 12 months. This study found that people who received interactive theory-based sessions (Arms 1 and 2) reported higher levels of condom use compared with STD clinic clients who received typical standard-of-care counseling. STD incidence was lower at all 5 sites among participants who received the enhanced interventions. At the Year 1 visit, there was a 20% reduction in STDs among participants who received the enhanced interventions. Although this study was not of sufficient size and duration to assess the impact of theory-based counseling sessions on HIV incidence, the study documented that enhanced counseling could be accomplished in an STD clinic setting and could result in decreased STD incidence.
Based on these results and those of other behavioral intervention trials, the CDC endorsed a program—Diffusion of Effective Behavioral Interventions—to disseminate effective behavioral interventions. Such effective behavioral interventions include:
The EXPLORE study is the only randomized trial conducted among HIV-uninfected MSM in the United States designed to test the efficacy of a behavioral intervention to prevent HIV infection that has used HIV acquisition as the primary study endpoint. At baseline, 48% of the 4295 men evaluated reported unprotected receptive anal intercourse and 55% reported having had unprotected anal insertive sex in the past 6 months. The men were randomized to receive a series of 10 one-on-one counseling sessions followed by a maintenance counseling session every 3 months (intervention group) or twice-yearly individual risk-reduction counseling (comparator group).
Although unprotected anal receptive intercourse with HIV-positive and HIV-unknown partners decreased significantly by 21% in the intervention group, there was only a modest reduction in HIV incidence compared with the standard counseling group (odds ratio: 0.82; 95% CI: 0.64-1.05), which was not statistically significant. Nevertheless, this study provided some evidence that behavioral interventions can provide risk reduction in the short term because the impact of the intervention was greatest in the first 12-18 months and waned thereafter. interventions for the prevention of HIV infection.
Some research has evaluated the impact of conditional cash transfers as a means to change behavior. Given the link between school attendance and a lower risk of HIV, a study conducted in Malawi evaluated the effect of small cash payments to keep adolescent girls and young women in school. In this randomized trial, school girls aged 13-22 years were randomly assigned to receive small cash incentives (up to US$15) for achieving high levels of school attendance or were in a control group with no incentives. Among the 1289 evaluable individuals, the weighted HIV prevalence after 18 months was 1.2% among girls who received the incentive and 3.0% in the control group (adjusted odds ratio: 0.36; 95% CI: 0.14-0.91). In a separate study, conducted in Tanzania, 2399 young adults were randomly assigned to receive high-value monetary incentives (up to US$60 over a year) to avoid engaging in unsafe sex, lower-value cash incentives (up to US$30), or were in a control arm. After 1 year, the high-value cash incentive was associated with a significant reduction in the risk of sexually transmitted infections that increase susceptibility to HIV. In this study, the provision of lower payments was not shown to be effective. Other studies evaluating the use of conditional cash transfers as a strategy to modify sexual behavior and reduce HIV risk are under way.
Interventions for People Who Inject Drugs
Behavioral interventions targeted toward people who inject drugs have also shown some success. One study identified 3 effective prevention strategies used in 5 cities to reduce HIV transmission through injection drug use: 1) establishing prevention programs when HIV seroprevalence is low, 2) administration of sterile injection equipment, and 3) community outreach to people who inject drugs. The CDC has also endorsed evidence-based behavioral interventions for HIV prevention.