FRIDAY, Nov. 12, 2004 (HealthDayNews) -- A vaccine designed to protect against two strains of the human papillomavirus that are leading causes of cervical cancer has been successful in a major trial.
It will next be tested in a large-scale study with the hope it can be widely available for use by the end of this decade, researchers report.
In a trial of more than 1,100 women aged 15 through 25 in North America and Brazil, three injections of the vaccine against HPV-16 and HPV-18 during a six-month period reduced the infection rate by 95 percent. And the vaccine provided complete protection against precancerous growths associated with the two strains, said a report in the Nov. 13 issue of The Lancet.
"Now we will go to a phase 3 trial in which we will enroll 15,000 women worldwide to see if we get the same protection rates and also if there are side effects we could not see in the smaller number of participants," said study author Dr. Diane M. Harper. She is director of the gynecological research group at Dartmouth Medical School's Norris Cotton Cancer Center.
A phase 3 trial is the last step in testing needed to gain regulatory approval for a drug or vaccine.
Worldwide, there are 470,000 new cases of cervical cancer and 230,000 deaths each year, most in developing countries, Harper said. The United States averages 13,000 new cases and 5,000 deaths annually, a toll kept relatively low by screening programs using Pap smear testing.
"Three decades of work shows that the virus causes the cancer," Harper said. "If we can protect against the kind of virus that causes it, we can make strong headway in controlling cervical cancer."
The vaccine used in the trial was made by a Belgian branch of GlaxoSmithKline. Recruitment for the larger trial began in May. "We hope to have 15,000 women enrolled by this January, and then we will follow them for four years," Harper said.
The vaccine is one of several at differing stages of development aimed at various strains of HPV, said Dr. Daron G. Ferris, a professor of family medicine and gynecology at the Medical College of Georgia, whose group participated in the trial. The group is also taking part in tests of a vaccine developed by Merck & Co. aimed at four HPV strains -- 6, 11, 16 and 18.
This "quadrivalent vaccine" not only protects against cervical cancer but also genital warts in women and penile cancer in uncircumcised men, Ferris said. Studies of the Merck vaccine are "slightly ahead" of those on the GlaxoSmithKline vaccine, he said.
When and if the four-strain vaccine is approved for widespread use, "we probably will target 10- to 12-year-old girls and probably boys as well," Ferris said. "They would be vaccinated before they have intercourse."
More information
For more on cervical cancer, visit the National Cancer Institute.
