Human papillomavirus (HPV) infection of the cervix can lead to cervical cancer. A vaccine designed to prevent cervical cancer and other diseases caused by infection with HPVs was approved for use in the U.S. in June 2006. This is the first vaccine to be developed against a known risk factor for the development of a cancer.While some HPV types infect the skin and cause benign warts and other lesions, about 40 types of HPVs can infect the genital tract. Genital HPV infection is very common in the general population; estimates suggest that up to 50% of all sexually active people will be infected at some point in their lives. In the majority of cases, the infection does not cause any symptoms, but in some women, HPV infection can progress to cause precancerous and cancerous lesions of the uterine cervix. HPVs that infect the genital area are also associated with other less common genital cancers in men and women such as cancers of the anus, vagina, penis, and vulva. HPV infection also causes genital warts in both men and women.
The most common HPV types that infect the genital area are HPV types 6, 11, 16, and 18. Among these, HPV types 6 and 11 are most commonly associated with benign lesions, such as genital warts and mild precancerous changes of the cervix. In contrast, HPV types 16 and 18 are the types found in the majority of cancers as well as in severe precancerous changes of the cervix. The vaccine, called Gardasil, targets these four common HPV types.
Gardasil, developed by Merck & Co., has been shown to be safe and 100% effective in preventing infection by these four common HPV types in young people who have not been previously infected with HPV. Its effectiveness is lessened for those who have already been exposed to the viruses.
The FDA has approved Gardasil for males and females aged 9-26. Another vaccine directed at HPV types 16 and 18 (the two HPV types most commonly associated with cervical cancer), known as Cervarix, manufactured by GlaxoSmithKline, has been approved for use in females aged 10-15. Ideally, vaccination should occur before youth become sexually active, since those who have not yet been infected with any HPV types will get the full benefit of the vaccine. However, it can also be useful in people who are already sexually active, since they may not be infected with HPV or may not be infected by all four HPV types covered by the vaccine.
Research is ongoing to determine whether the vaccine has any beneficial effects in older women, and its safety for use in pregnant women has not yet been determined. It is also not known if the vaccine confers lifelong immunity, since long-term study results are not yet available.
Since Gardasil only targets the four major types of HPV that infect the genital tract, it cannot protect against all causes of HPV. HPV types 16 and 18 are the causes of about 70% of all cervical cancers, and HPV types 6 and 11 cause about 90% of genital warts. All women, even those who have received the vaccine, should still undergo regular cervical cancer screenings.
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