Carraguard Does Not Prevent Vaginal Transmission of HIV
A vaginal microbicide based on a seaweed-derived compound failed to prevent HIV infection during a randomized, placebo-controlled, double-blind Phase III trial in South Africa, researchers reported Thursday.
The study enrolled 6,202 sexually active, HIV-negative female participants age 16 and older at three sites. Subjects were asked to use an applicator of gel plus a condom during every vaginal sex act. The women were screened for HIV every three months for up to two years.
Among 3,011 women given the carrageenan-based gel, Carraguard, HIV incidence was 3.3 per 100 woman-years. That compares to an HIV incidence of 3.8 per 100 woman-years among the 2,994 women given the placebo, which was a methylcellulose gel. The covariate-adjusted hazard ratio was 0.87, a nonsignificant difference. In addition, there was no significant difference in time to seroconversion.
On the basis of applicator testing, researchers estimate that a gel was used in just 42.1 percent of sex acts (41.1 percent Carraguard, 43.1 percent placebo). However, there was no significant difference in seroconversion based on frequency of use.
“Carraguard is unlikely to have a meaningful protective effect as used by study participants,” concluded researchers. Given the low adherence rate among subjects, that could suggest “even a highly efficacious coitally-dependent product will have insufficient effectiveness in real-life settings,” they wrote.
Ultimately, a combination of partially effective prevention approaches targeting specific populations would “involve behavioral, biomedical, and structural interventions, each designed to reinforce the effect of the other,” suggests an accompanying editorial.
The full report, “Efficacy of Carraguard for Prevention of HIV Infection in Women in South Africa,” and the editorial, “HIV Prevention Research: The Ecstasy and the Agony,” were published in The Lancet (2008;372(9654):1977-1987 and 1932-1933).
Date of Publication
Clinical Trials Heterosexual Transmission HIV/AIDS Prevention Microbicides Women
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