Abstract #294  -  Biomedical Strategies for HIV Prevention
Authors:   Presenting Author:   Dr. Hunter Handsfield - Univ of Washington and Battelle Research
Additional Authors:
Aim: This presentation summarizes current and potential biomedical strategies to prevent HIV transmission, and the importance of integrating biomedical with behavioral methods.
Method / Issue: Improvements in treatment for HIV/AIDS and evolving data on HIV transmission and behavioral prevention strategies have led to rising emphasis on biomedical approaches to prevent HIV. The determinants of the population prevalence of an infectious disease can be expressed as Ro = βcD, in which Ro is the reproductive rate of infection in the population, β denotes transmission efficiency, c the frequency of interactions that result in transmission (e.g., the rate of sex partner change), and D the mean duration of infectivity. Biomedical strategies to prevent HIV can be conceptualized as those whose primary effect is to limit β, the efficiency of HIV transmission.
Results / Comments: The male condom is the most widely employed biomedical prevention device and will remain a mainstay of HIV prevention for the foreseeable future. The female condom has promise but limited acceptance. Other barrier devices, such as diaphragm and cervical cap, probably reduce HIV transmission efficiency but are limited by numerous logistical barriers. Vaginal microbicides carry the important theoretical advantage of control by women, but identification of effective, well tolerated compounds and delivery vehicles has proved difficult. Rectal microbicides, for use by receptive anal sex partners, carry their own challenges. Male circumcision reduces HIV transmission by about 50% and could have dramatic population-level prevention benefits; the barriers to widespread implementation are daunting but probably can be surmounted in most cultures. Antiretroviral therapy (ARV) is effective and widely employed in the prevention of mother-to-child HIV transmission, and evolving data document the long-assumed benefit of ARV in preventing sexual transmission of HIV. Post-exposure prophylaxis with ARV therapy prevents infection among occupationally exposed health care providers and probably prevents sexual transmission, but its population level impact is trivial. Pre-exposure prophylaxis is promising and under investigation, but may be limited by logistical considerations and concerns about effects on HIV susceptibility to ARV drugs. Treatment and prevention of non-HIV sexually transmitted infections is theoretically promising. However, although supported by a single population-based trial, other controlled trials demonstrated no benefit in HIV prevention. Antiherpetic treatment of HSV-2 infected persons failed to prevent incident HIV infection compared with controls; results are imminent for a trial of antiherpetic therapy to prevent HIV transmission by dually infected persons. The prospects are dim in the next several years for effective prophylactic immunization, the ultimate biomedical prevention strategy of choice.
Discussion: The efficacy of some biomedical HIV prevention strategies and the future promise for others do not challenge the centrality of behavioral prevention. Indeed, biomedical interventions carries own behavioral imperatives. Despite >90% biological efficacy of condoms, population level success is entirely dependent on enhancing the behavior of consistent condom use. As biomedical interventions are increasingly employed, the potential for behavioral disinhibition – increased risky behavior as a consequence of perceived lower risk, as occurred in some populations in response to improved clinical outcomes from ARV therapy – is a high priority for behavioral research. Finally, optimizing provider behaviors in implementing biomedical strategies is a core element of type II translational research.
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