Merck vaccine shown to block cervical cancer, genital warts

An enhanced version of an experimental vaccine against human papillomavirus was 90% effective in blocking four types of the sexually transmitted disease, according to a study published Wednesday. Merck's Gardasil was designed to block HPV types 16 and 18, which cause about 70% of cervical cancer cases, and types 6 and 11, responsible for about 90% of genital wart cases. "It's the first time we show efficacy for the most broad-coverage vaccine in development," says Eliav Barr, who runs Merck's HPV vaccine development program. Since most HPV infections clear on their own, vaccine developers are focusing on those types that cause persistent or long-term infection, said Barr. In late 2004, New Jersey-based Merck published results showing that an earlier vaccine candidate targeting only HPV 16--the cause for about 50% of cervical cancers--prevented infection in 94% of women over a four-year period. Around that same time, GlaxoSmithKline announced its vaccine against types 16 and 18 prevented persistent infection in hundreds of women ages 15-25. The current study involved 552 women ages 16-23 in the United States, Brazil, and Europe. Half the women were given Gardasil, and all were examined for HPV infection, genital warts, and precancerous lesions over the study's 2.5-year follow-up. Among women in the control group, 36 developed an HPV infection or one of the diseases it causes. Four vaccine recipients were infected with HPV, but none contracted cervical cancer, precancerous lesions, or genital warts related to those types. Gardasil is currently in final-stage human testing of more than 25,000 women worldwide. Those results are expected in the second half of 2005. Each year nearly half a million women worldwide develop cervical cancer, and about half of them die from it. Cervical cancer affects about 15,000 U.S. women, and about 5,000 die annually. (AP)