NEW YORK -- December 4, 2008 -- The candidate vaginal microbicide gel Carraguard (R), a carrageenan-based compound, does not protect women from HIV infection, according to an article appearing in the December 6 edition of The Lancet.
In a randomised, placebo-controlled trial, Stephanie Skoler-Karpoff and Barbara Friedland, Population Council, New York, New York, and colleagues assessed the carrageenan-based gel developed by the Population Council.
The trial took place at 3 sites in South Africa and involved 6,202 sexually active, HIV-negative women who were assigned to receive the carrageenan-based gel (n = 3,103) or a placebo gel of methylcelluose (n = 3,099).
The women were instructed to use 1 applicator of gel plus a condom for each vaginal sex act. Participants were followed up for up to 2 years. The women visited a clinic every 3 months, where patients were tested for HIV presence and pregnancy, underwent pelvic examinations, had risk reduction counseling, and were treated for curable sexually transmitted infections and symptomatic vaginal infections. The primary outcome of the trial was time to seroconversion.
The researchers found that HIV incidence was 3.3 per 100 woman-years in the carrageenan-based gel group (134 infections) and 3.8 per 100 woman-years in the placebo group (151 infections), with no significant difference in the time to serocoversion.
Rates of self-reported gel use (96.2% carrageenan-based gel, 95.9% placebo) and condom use (64.1% both groups) at last sex acts were similar in both groups. On the basis of applicator testing, however, gel was estimated to have been used in only 42.1 % of sex acts on average (41.1% carrageenan-based gel, 43.1% placebo).
Adverse events were similar in both groups; adverse events related to gel use and serious adverse events were similar in both groups.
"This study did not show [the carrageenan-based gel's] efficacy in prevention of male-to-female transmission of HIV, although no safety concerns were recorded," the authors write.
"Low levels of gel use could have compromised the potential to detect a significant protective effect. Although the results from this and other completed microbicides efficacy trials have been disappointing, the search for female-controlled HIV-prevention methods must continue."
In an accompanying comment, Willard Cates, MD, and Paul Feldblum, MD, Family Health International, Durham, North Carolina, say, "Whenever we develop effective new tools for HIV prevention, no single approach to prevention will suffice. Rather a combination of partly effective prevention approaches will be bundled into packages targeted to specific populations. This bundling will involve behavioural, biomedical, and structural interventions, each designed to reinforce the effect of the other. The cumulative influence of combination prevention is our hope for thwarting the spread of HIV."
SOURCE: The Lancet
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