In May 2006, an advisory committee to the U.S. Food and Drug Administration (FDA) voted unanimously to recommend approval of Gardasil, a preventive vaccine developed by Merck & Co. Clinical trials have demonstrated that Gardasil is safe and effective for the prevention of cervical cancer and dysplasia of the cervix, vulva, and vagina. A similar vaccine, Cervarix, is being developed by GlaxoSmithKline.
Gardasil protects against four types of HPV: types 6, 11, 16 and 18. HPV types 16 and 18 account for an estimated 70% of cervical cancer cases and can lead to vulvar and vaginal cancers. These HPV types are also believed to be the most common causes of anal cancer. HPV types 6 and 11 account for most genital wart cases and low-grade cervical and anal abnormalities.
The safety and effectiveness of Gardasil in HIV-positive people have not been determined. Similarly, the effectiveness of Gardasil as a preventive vaccine against cancer and pre-cancerous lesions of the anus, in HIV-negative or HIV-positive men or women, has not been determined.
Gardasil and Cervarix are most likely to be effective in people who have not yet been exposed to HPV. Because HPV is so easily and frequently transmitted via sexual activity, this means that the vaccines will likely need to be given to people before they become sexually active (for example, school-aged children). In other words, it is not clear if these vaccines will be useful to sexually active adults, including those infected with HIV.
For people who have anal (and possibly cervical) dysplasia caused by HPV, therapeutic vaccines are being studied. These vaccines are being developed to boost the immune response to the virus. This may help reduce the need for invasive treatments (such as those reviewed in the last section of this lesson) and/or reduce the risk of dysplasia recurring after successful treatment. One recent study involving Nventa Biopharmaceuticals' therapeutic vaccine HspE7 concluded that it is safe and potentially effective in HIV-positive men and women with anal dysplasia.
As for preventing the sexual transmission of HPV, a study published in June 2006 in the New England Journal of Medicine concluded that condoms can help reduce the risk of HPV transmission. The study, conducted by researchers at the University of Washington in Seattle, refutes the results of earlier analyses concluding that condom use does not reduce the risk of HPV infection.
According to the study results, women whose partners used condoms for all instances of vaginal intercourse were 70% less likely to acquire HPV than were women whose partners used condoms less than 5% of the time. Even women whose partners used condoms more than half the time had a 50% risk reduction, as compared with those whose partners used condoms less than 5% of the time. What's more, none of the women who reported consistent condom use had evidence of precancerous or cancerous cervical lesions, compared to some reports of precancerous lesions found in women who never or inconsistently used condoms for vaginal intercourse.
While this study did not look at the effectiveness of condoms for the prevention of anal HPV infection, the reduced risk of HPV infection via vaginal intercourse when condoms are used correctly and consistently suggests a similar benefit for men and women who engage in anal intercourse.
Regular anal/vaginal exams and Pap smears are crucial. While they can't prevent warts or dysplasia from occurring, they can help catch them before they progress and cause greater problems.
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