Merck on Wednesday at the 47th Annual Interscience Conference on Antimicrobial Agents and Chemotherapy in Chicago released data showing that its human papillomavirus vaccine Gardasil partially prevents infection of 10 HPV strains in addition to the four HPV strains targeted by the vaccine, the AP/Philadelphia Daily News reports (Johnson, AP/Philadelphia Daily News, 9/20). Gardasil in clinical trials has been shown to be 100% effective in preventing infection with HPV strains 16 and 18, which together cause about 70% of cervical cancer cases, and about 99% effective in preventing HPV strains 6 and 11, which together with HPV strains 16 and 18 cause about 90% of genital wart cases among women not already infected with these strains (Kaiser Daily Women's Health Policy Report, 9/19).

According to Dow Jones/CNNMoney.com, an analysis of two large Phase III clinical trials of Gardasil found that the vaccine showed cross-protection against precancerous lesions caused by an additional 10 HPV strains that cause about 16% of cervical cancers in Europe and 22% of cervical cancers worldwide. The clinical trials involved administering either three doses of Gardasil or a placebo to girls and women ages 15 to 26. The participants also underwent cervical-vaginal sampling and Pap tests at the beginning of the study and at six- to 12-month intervals for up to 48 months (Fontaine, Dow Jones/CNNMoney.com, 9/19).

The new data found that Gardasil reduced by nearly two-thirds the incidence of precancerous lesions caused by HPV for three of the most common HPV strains found in North America after strains 16 and 18. The three strains cause about 11% of cervical cancers worldwide. According to the AP/Daily News, the finding means that Gardasil provides at least partial protection to 90% of HPV strains that cause cervical cancer.

Eliav Barr, head of infectious disease and vaccine research at Merck, said the new finding could prevent 30,000 to 40,000 cervical cancer cases annually. Stephanie Blank, a gynecological oncologist at the New York University Cancer Institute, said the finding could encourage increased use of Gardasil in developing countries, where some of the additional strains are widespread. Gardasil currently is approved for sale in 85 countries and is pending approval in another 40 countries. There are about 9,710 new cervical cancer cases and 3,700 deaths annually in the U.S., and about 500,000 new cases and 233,000 deaths worldwide, the AP/Daily News reports (AP/Philadelphia Daily News, 9/20).