Reducing infectiousness of HIV-infected individuals is among key biomedical prevention strategies

August 05, 2008

With no HIV vaccine available for the foreseeable future, focus must be on proven biomedical HIV prevention methods such as male condoms, male circumcision and prohphylactic antiretroviral (ARV) drugs to prevent mother-to-child transmission. Oral and vaginal ARVs for both pre-exposure prophylaxis and to reduce infectiousness among HIV-positive individuals are being assessed, and are showing great promise. These are among the conclusions of Dr Nancy Padian, Women's Global Health Imperative, RTI International, San Francisco, CA, USA, and Dr Ward Cates, Family Health International, North Carolina, USA, and colleagues, authors of the second paper in the Lancet Series on HIV prevention.

The authors say that prophylactic treatment, as with other sexually transmitted infections, should target infected individuals, and, should it prove effective, issues related to resistance and distribution will have to be considered before scale up. New designs are being trialled to improve uptake of the female condom, since studies suggest it is as effective as the male condom at preventing HIV transmission. The female diaphragm with male condom use did not show extra protection compared with male condom use alone. However, if safe and effective against HIV, BufferGel, an antimicrobial gel, will be combined with a disposable, one-size-fits-all, clear diaphragm which could be an effective barrier to HIV.

Controlling other STIs to prevent HIV infection is also vital since transmission within partnerships is made easier by concurrent infection with various STIs, eg, genital ulcerative diseases such as syphilis and herpes (herpes simplex virus-2 / HSV2). However, trials assessing herpes treatment to prevent HIV infection have so far not shown any benefit, and the authors say even if they did, "Introduction of such interventions at a population level is probably not feasible, especially since the prevalence of HSV-2 infection is high in many low-resource settings."

Male circumcision (MC) has been shown to reduce the risk of HIV transmission by 58%, and studies so far suggest that while some men increase their risky behaviour afterwards thinking they are safer, others do not. But men must wait for their wounds to heal, as one study showed MC did not protect female partners from HIV infection. Since MC is a one-time-only procedure, it could be very cost effective; one study estimates that in Gauteng Province, South Africa, the cost per HIV infection averted could be as low as US$181, based on a cost of $47 per procedure. The authors say: "A 100% uptake of MC could avert an estimated 2 million deaths during 10 years in sub-Saharan Africa and 5.7 million infections during 20 years."

As well as scale-up of ARV treatment to prevent mother-to-baby transmission, provision of contraception for HIV-positive women who do not want to become pregnant will also be an effective HIV-prevention measure. And for all interventions, research is needed on both how to improve and how to measure adherence. Despite the probability that no vaccine will be available for many years, phase III trials of candidate vaccines, and also microbicides, often go ahead because "we simply do not know what does and does not work, and additionally we will learn valuable lessons from the trials, which we have."

The authors stress that a single solution will not be found for prevention. Instead, partially effective interventions will be aggregated into combination prevention packages and targeted to specific individuals. They conclude: "As we approach the era of antiretroviral-based prevention (alone or as part of a combined package) to reduce HIV acquisition in uninfected individuals and to decrease HIV infectiousness in infected individuals, we should exercise restraint and not again set standards so high that moderate-level prevention strategies, which could offer measurable individual and population benefits, are destined not to demonstrate efficacy."
Dr Nancy Padian, Women's Global Health Imperative, RTI International, San Francisco, CA, USA (attending conference) (cell) T) +1 415-279-8241 E)

Alternatively, Dr Padian is staying at Camino Real Hotel Mexico City during the conference, T) +52 55 5 263-8888

Dr Ward Cates, Family Health International, Research Triangle Park, North Carolina, USA T) +1 919-405-1404 E)


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