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The recently-approved vaccine against human papilloma virus (HPV) may have substantial benefits beyond preventing infections that might lead to cervical cancer and genital warts. New research shows it also protects against abnormalities that can lead to vaginal, vulvar, and anal cancers. There are also tantalizing hints that the vaccine may one day have a role in preventing some head and neck cancers.

The vaccine, Gardasil, is manufactured by Merck. It targets 4 types of HPV: HPV 16 and 18, which together are responsible for about 70% of cervical cancer cases, and HPV 6 and 11, which together cause about 90% of cases of genital warts.

These types of HPV can be passed from person to person through sexual contact.

The new findings are published in 3 separate studies in this week's New England Journal of Medicine.

One study deals specifically with pre-cancerous changes of the cervix and confirms information federal health officials used to approve Gardasil last year. The study is the formal report of some of those findings by an international group of cancer researchers known as the FUTURE II Study Group.

Their results involved more than 10,000 women between the ages of 15 and 26. About half the women were given the Gardasil vaccine, while the other half received a placebo. They were followed for an average of 3 years.

The study showed that the vaccine was 98% effective in preventing the cell changes (lesions) in the cervix caused by HPV 16 and 18 that often lead to cervical cancer.

"Everyone who gets cancer goes through a pre-cancerous stage," says Kevin Ault, MD, an associate professor of obstetrics and gynecology at Emory University School of Medicine in Atlanta and one of the study's authors. "We spend about $3 billion each year to find and treat these pre-cancerous stages caused by some type of HPV."

Despite these strong results, experts say women still need to get regular Pap tests to look for cervical cancer.

The HPV types targeted by the vaccine aren't the only ones that can cause cancer, so even vaccinated women aren't 100% protected from this disease. Furthermore, it's been only about 5 years since studies began; the participants are still being followed to see how long the vaccine's protection will last.

And, the vaccine only worked in women and girls who were not already infected with HPV 16 or 18. That's why federal health officials and the American Cancer Society recommend giving Gardasil routinely to 11- and 12-year-old girls, and allow it for girls as young as 9. Vaccinating girls before they become sexually active and have a chance to catch HPV gives them the best chance of being protected by the vaccine.

A second study in the same issue of the journal shows that vaccinated women and girls likely will reap additional benefits aside from possible cervical cancer protection. Another international group of researchers, the FUTURE I Investigators, report that Gardasil prevented 100% of pre-cancerous changes associated with HPV types 6, 11, 16, or 18 in or around the vagina, vulva, and anus.

They studied more than 4,500 women and girls between the ages of 16 and 24, of whom half were given the vaccine and the other half a placebo. Like participants in the FUTURE II study, these women were followed for an average of 3 years.

In that time, none of the vaccinated women developed cervical, vaginal, vulvar, or anal lesions (which could lead to cancer), or genital warts caused by the 4 HPV types in the vaccine.

In this case, though, women still seemed to have some protection even when they already had one of the HPV types targeted by the vaccine. Gardasil prevented 73% of pre-cancerous vaginal, vulvar, and anal changes and warts in these women. It also seemed to cut down on problems caused by HPV types other than those it targets.

The third study isn't about HPV vaccination, but about HPV's role in cancers of the mouth and throat (known as oropharyngeal cancers). These cancers are often linked to smoking and drinking alcohol.

Researchers from the Johns Hopkins Bloomberg School of Public Health found that HPV 16, one of the strains targeted by Gardasil, is present in a large percentage of these tumors. This may help explain why some people who never smoke or drink still develop this disease.

It also raises the possibility that HPV vaccination might help cut down on these head and neck tumors. More research will be needed to find out if that is the case.

"It will be important to monitor whether any potential reduction in head and neck cancers will occur among those who are just now starting to receive the vaccine," says Debbie Saslow, PhD, director of breast and gynecological cancers at the American Cancer Society. "While there is no evidence yet that the vaccine will reduce head and neck cancer incidence, it is reasonable to expect that long-term data will show a benefit."

Citations: Quadrivalent Vaccine against HPV to Prevent High-Grade Cervical Lesions Published in the May 10, 2007 New England Journal of Medicine (Vol. 356, No. 19: 1915-1927). Author: The FUTURE II Study Group.

Quadrivalent Vaccine against Human Papillomavirus to Prevent Anogenital Diseases Published in the May 10, 2007 New England Journal of Medicine (Vol. 356, No. 19: 1928-1943). First author: Suzanne M. Garland, MD, Royal Women's Hospital and the University of Melbourne, Melbourne, Australia.

Case–Control Study of Human Papillomavirus and Oropharyngeal Cancer Published in the May 10, 2007 New England Journal of Medicine (Vol. 356, No. 19: 1944-1956). First author: Gypsyamber D'Souza, PhD, Johns Hopkins Bloomberg School of Public Health.