Scientists say they have created the first vaccine that appears to be able to prevent cervical cancer by making people immune to the sexually transmitted virus that causes most cases of the disease. The experimental vaccine will not be available to the public for several years, but if it is successful, it could sharply reduce the rates of cervical cancer, which kills 225,000 women worldwide each year.

The new research, "A Controlled Trial of a Human Papillomavirus Type 16 Vaccine," is published in today’s New England Journal of Medicine (2002;347:1645-1651). The study followed 2,392 young women who were given either the vaccine or placebo shots. The vaccine was 100 percent effective. In 17 to 27 months of follow-up, no vaccinated women developed infections or precancerous growth from the virus; 41 non-vaccinated women became infected, including nine with precancerous cervical growths. The study was carried out by researchers from 16 universities and Merck Research Laboratories. Merck & Co. made the vaccine and paid for the research.

Researchers cautioned the vaccine would not do away with the need for Pap tests. Most cervical cancer deaths occur in the developing world where women do not have regular Pap tests. "For individuals in countries with no screening, vaccination is a life-saver," said Dr. Kathrin U. Jansen, Merck’s senior director of microbial vaccine research. In the United States, where 50 million to 60 million Pap tests are done annually, a great benefit would be a drop in the number of women who, because of the virus, have abnormal Pap tests and need repeated exams. By preventing the infections and abnormal growths, a vaccination could spare nearly 1 million women a year the worry and expense of additional unpleasant procedures.

Almost every case of cervical cancer is caused by human papillomaviruses, which are sexually transmitted, very common and hard to avoid. Condoms may lower the rate of transmission but do not prevent it.

The new vaccine was designed to test whether people could be made immune to one type of virus, which causes 50 percent of cervical cancers. The vaccine Merck hopes to market will protect patients against HPV-16 and HPV-18, which together cause 70 percent of all cases of cervical cancer. It will also protect against the HPV varieties that cause 90 percent of genital warts. The wart protection was included to "give incentive to young men to also take the vaccine," Jansen said.

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