HPV Vaccine Protects Against Genital Warts and Precancerous Growths

Results from a recent international study indicate that the vaccine Gardasil® (quadrivalent human papillomavirus [types 6, 11, 16, 18] recombinant vaccine) protects against genital warts and low-grade precancerous changes to the cervix, vulva, and vagina. These findings were published in the journal BMJ.

Human papillomaviruses (HPV) consist of more than 100 different viruses. Some types of HPV cause warts on the hands or feet; others cause genital warts; and some have been linked with cancer, most notably cervical cancer.

Gardasil prevents infection with four types of HPV—types 6, 11, 16, and 18. HPV types 16 and 18 cause roughly 70% of all cases of cervical cancer, and HPV types 6 and 11 account for roughly 90% of genital warts. Gardasil was approved by the U.S. Food and Drug Administration (FDA) in June 2006.

Previous studies have shown that Gardasil protects against high-grade precancerous changes to the cervix, vulva, and vagina. High-grade changes are those that are the most likely to progress to invasive cancer if not treated.

Less is known about how vaccination will affect the risk of low-grade precancerous changes (cervical, vulvar, or vaginal intraepithelial neoplasia grade 1). Although many low-grade changes will resolve on their own without treatment, these changes require follow-up and may be a source of anxiety and expense.

To further understand how effectively Gardasil may protect against genital warts as well as low-grade lesions, researchers conducted a study including almost 18,000 women from around the world. Participants were ages 16-26 years at enrollment.

One group of women was given three doses of Gardasil, and the other group received a placebo. HPV-related outcomes were compared between groups:

• Gardasil was 96-100% effective in preventing low-grade lesions or genital warts related to the HPV types the vaccine is targeted against (types 6, 11, 16, and 18).
• When looking at all lesions regardless of HPV type, the efficacy of Gardasil was 30% for low-grade cervical changes; 75% for low-grade vulvar changes, 48% for low-grade vaginal changes, and 83% for genital warts.
• Protection was sustained through the four years of follow-up.

The researchers concluded that Gardasil provides sustained protection against low-grade cervical, vulvar, and vaginal lesions related to HPV types 6, 11, 16, and 18. Because such lesions affect patient health and healthcare cost and may cause anxiety, preventing them could be an important contribution to public health.

Reference: The FUTURE I/II Study Group. Four year efficacy of prophylactic human papillomavirus quadrivalent vaccine against low grade cervical, vulvar, and vaginal intraepithelial neoplasia and anogenital warts: randomised controlled trial. BMJ. 2010;341:c3493.

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