There's new hope that cervical cancer could be progressively eradicated in a global campaign, much like the ones against smallpox and polio.
Researchers say a second experimental cervical cancer vaccine appears to broadly protect against infection and risky precancerous conditions for more than two years.
The study, which was conducted in the United States and Brazil, indicates that patients given the vaccine sustained a high level of immune response against the virus that spreads cervical cancer, and that it would prevent infection for many years. Whether revaccination ultimately would be needed must be determined by an additional, longer trial, researchers said.
Details appear in Friday's issue of the British medical journal The Lancet. The study was supported by GlaxoSmithKline PLC, the vaccine's manufacturer.
Worldwide, 511,000 women are stricken with cervical cancer each year, and about half die. It is the leading cancer killer among women in the developing world.
In the U.S., reports CBS News Correspondent Melissa McDermott, cervical cancer strikes about 15,000 women each year, and about 5,000 die annually.
Cervical cancer is caused by infection with human papilloma virus, or HPV, which is spread through sex. There are dozens of HPV strains, but two of them — HPV-16 and HPV-18 — account for more than 70 percent of cervical cancers.
The GlaxoSmithKline vaccine is designed to prevent infection from both major strains. In the study, researchers recruited 1,113 women at 32 clinics beginning in 2000. The participants, ages 15-25, had no signs of infection. Their cases were followed for 27 months.
Of the women who received the vaccine, 94 percent were protected from infection and the virus that causes most cervical cancers, McDermott reported.
About half of the women received the vaccine, while the rest received a placebo.
None of the vaccinated women developed infections or cervical precancerous lesions, said Dartmouth obstetrician Diane M. Harper, the study's lead author. The vaccine also protected 93 percent against conditions that lead to abnormal Pap tests, she said.
In the placebo group, 10 women developed HPV-16 infections and four developed HPV-18 infections by the study's seventh month.
Last May, GlaxoSmithKline started enrolling 15,000 women for a final four-year vaccine trial, although government approval could come sooner.
Washington also has given vaccine development rights to Merck & Co., and officials said the research is being conducted cooperatively.
On Nov. 1, Merck announced that its HPV-16 vaccine works for at least four years. It is conducting its own large-scale trial of a vaccine that covers both HPV-16 and 18. Results are expected next year.