New results indicate the vaccine might work just as well in women aged 24 to 45 years, Merck said in a press release. In clinical trials, the vaccine was shown to be 100 percent effective in protecting against cervical cancer in the age group of 9-26 years. HPV strains 6 and 11 are implicated in causing cervical cancer, while strains 16 and 18 cause genital warts as well.

In a new study presented at the 24th International Papillomavirus Conference in Beijing, Merck revealed that Gardasil was able to prevent infections caused by HPV types 16 and 18 in 83 percent of the cases. The conditions prevented by Gardasil included external genital lesions, cervical abnormalities and pre-cancers.

The international study involved 3,800 women, aged 24 to 45 years. All participants did not have any history of hysterectomy or biopsy-diagnosed cervical HPV disease in the last five years. Additionally the women also did not have history of genital warts and LEEP (loop electrosurgical excision procedure).

The women were randomly assigned to receive Gardasil or placebo over six months. The study followed the women for up to 20 months after they received the last shot.

The results showed that Gardasil was able to reduce persistent infection, cervical abnormalities and pre-cancers, and external genital lesions in 91 percent of cases as compared to a placebo. Adverse effects noted in the Gardasil group included pain and swelling and injection-site allergic reactions.

“Women remain at significant risk for acquiring HPV infections and developing HPV-related diseases throughout their lifetime,” said Eliav Barr M.D., executive director of Biologics Clinical Research and head of the HPV Vaccine Program, Merck Research Laboratories. “These data build on the clinical program for Gardasil and will help us to understand the potential benefit that Gardasil may have in women through age 45.”

Merck said that it will be presenting the new data to the US Food and Drug Administration for review and will seek approval for expanded use of Gardasil. The latter was approved for use in girls and women aged 9 to 26 years on June 8, 2006. Gardasil is also approved for use in 85 countries across the world.

The American Cancer Society estimates about 11,150 cases of invasive cervical cancer will be diagnosed in the United States this year and about 3,670 women will die from cervical cancer in the United States. Use of Pap smears on a large scale has reduced the mortality from cervical cancer because of early detection.

Gardasil costs $120 per dose and amounts to $360 for a full 3-month regimen.