Biomedical Interventions to Prevent HIV Infection: Evidence, Challenges, and Way Forward

Published as the second in a series of six articles about HIV prevention in The Lancet (Vol. 372, pp. 585-599), this review discusses the state of biomedical HIV prevention research. The authors focus on sexual transmission, classifying prevention methods by the specific mechanism of action rather than the mode of delivery. They review physical barrier methods, control of other sexually transmitted infections (STIs), male circumcision, topical antimicrobial (microbicide) preparations, the prophylactic use of antiretroviral drugs (oral and topical), and HIV vaccines. For each of these methods, they describe the available evidence for efficacy or effectiveness, make recommendations for use, and suggest future research needed. They also review levels of evidence for effectiveness for each method.

In brief, this assessment reveals that no HIV vaccine or topical prophylaxis will be available in the foreseeable future. Thus far, the authors explain, the only biomedical interventions that are effective in prevention are use of male condoms, male circumcision, and prophylactic use of antiretroviral drugs or contraception to prevent unwanted pregnancies to reduce mother-to-child transmission. In this context, they say, there is no single solution for prevention; "[i]nstead, partially effective interventions will be aggregated into combination prevention packages and targeted to specific individuals."

The authors stress that communication strategies should play a role in moving forward. "For example, to avoid risk compensation and to increase adherence, biomedical methods should be inextricably implemented together with behavioural interventions. Likewise, biomedical interventions, such as male circumcision, offer a unique opportunity for risk reduction counselling. Rather than trying to control for the effect of behaviour on biomedical methods, future studies should embrace this integration and use creative designs to examine strategies that offer a variety of prevention methods."

There are challenges associated with assessing progress made with these efforts. For instance, behavioural factors operating at the community level, such as inadequate adherence and sexual risk compensation, might offset any positive effect at the population level of an intervention that has been proven to be effective in a trial. Thus, "[a]ll components of the intervention (biomedical and behavioural) should be clearly defined, replicable, and suitable for rigorous assessment." However, assessing multicomponent interventions, especially those postulated to have modest effects, can be complicated by factors such as the ability to distinguish the marginal effect of the new intervention over that of an intensive prevention package, the nature of the control group, and separation of the effect of adherence from the potential of the intervention. The take-home message, then, is as follows: "To scale up effective interventions, the level of evidence needed requires more than biological effectiveness of the intervention; operational considerations, such a long-term adherence, the possibility of harm, and sustainability have to be considered."

Note: this article is freely accessible with a complimentary registration/log-in to the Lancet. Click here for access.

Click here to access "Putting prevention at the forefront of HIV/AIDS", by Richard Horton and Pam Das. This Introductory essay to the series of which the above-summarised article is a part provides background and the rationale for this Lancet effort to provide a simplified roadmap for countries seeking to develop their own evidence-driven strategies to respond to AIDS. The Lancet series was launched at the International AIDS conference in Mexico City, Mexico, in August 2008.