Cervical barrier methods

In addition to microbicides, which function as a chemical barrier, interest has grown in examining other female-initiated barrier methods that may offer some physical protection against the transmission and acquisition of HIV

infection. The female condom is a lubricated polyurethane sheath with a ring on either end that is inserted into the vagina before sexual intercourse. It has been studied primarily for its effectiveness in preventing pregnancy and STIs other than HIV. Laboratory studies and clinical trials have shown that the female condom provides an effective barrier to organisms smaller than those that cause most STIs, and it is at least equivalent to male condoms in terms of preventing gonorrhoea, trichomoniasis and chlamydia (111). There have been no clinical trials specifically assessing the efficacy or effectiveness of the female condom in preventing HIV infection. However, based on studies in which STI prevention and pregnancy prevention were assessed, it is estimated that the female condom is 94-97% effective in reducing the risk of HIV infection if used correctly and consistently (111). The female condom may be a more attractive choice than male condoms for some women because it resists breaks and tears and covers both the internal and external genitals, which are primary sites of STI lesions (112-114).

Findings from basic and clinical research indicate that HIV susceptibility may not be equally distributed across the epithelial surfaces in the vagina and that the cervix may be particularly vulnerable to HIV and STI transmission (115,116). This has led to an interest in the risk-reduction potential of cervical barrier methods, such as the diaphragm and cervical cap. These barriers are made of soft latex or silicone and are used with spermicidal cream or jelly and then inserted into the vagina to fit over the cervix. Several observational studies have indicated that when the diaphragm is used in conjunction with spermicide it may offer protection against some STIs and their associated sequelae (117-121). As of March 2006, seven clinical trials at various stages (phase I to phase III) were under way to examine the diaphragm's effectiveness in preventing STIs (122). Of these studies, the furthest along is the Methods for Improving Reproductive Health in Africa Trial, a phase III trial that will measure the effectiveness of the diaphragm when used with Replens lubricant gel in preventing heterosexual acquisition of HIV infection among women in South Africa and Zimbabwe (123).

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