THURSDAY, April 6, 2006 (HealthDay News) -- An experimental cervical cancer vaccine remains effective for nearly five years, and may protect women against more types of cancer-causing viruses than originally thought, researchers report.
"At 4.5 years, the vaccine was still protecting everyone," said study author Dr. Diane M. Harper, a professor of community and family medicine and obstetrics and gynecology at Dartmouth Medical School.
The study, reported in the April 6 online issue of The Lancet, is a follow-up on some of the more than 1,100 women who participated in a previous study gauging the effectiveness of the vaccine. Called Cervarix, the vaccine is under development by drug giant GlaxoSmithKline.
In this latest effort, Harper's team tracked 776 of those women, following them for up to 53 months. The women had received either three doses of the vaccine or three doses of placebo.
A specific type of infectious pathogen, called the human papilloma virus (HPV), is credited with causing most cervical cancers. Cervarix is designed to protect against HPV types 16 and 18, Harper said, which account for about 70 percent of cervical malignancies.
However, Harper's team found the vaccine also conferred protection against two other HPV types, 45 and 31, which can also trigger cervical cancer.
At the end of the 4.5 years, all the women still tested positive for having been immunized with HPV 16 and 18, the researchers found. And Harper noted that "their antibody levels [which develop after a vaccine is administered] on average did not decrease," meaning the vaccine seems to have conferred ongoing protection against these cancer-causing viruses.
Cervical cancer is the second most common malignant disease in women globally, the authors note, and it often is diagnosed at a younger age than other cancers. The main cause of cervical cancer is continuous infection with human papilloma viruses, especially HPV 16 and 18, which are spread by sexual contact.
Harper said women who got Cervarix didn't report any more long-term problems (such as thyroid problems) compared to those who received a placebo injection.
The vaccine's apparent long-term effectiveness is promising, said Rachel Winer, a University of Washington, Seattle, research scientist and HPV researcher. Once a cervical cancer vaccine hits the market, young women in their late adolescence or early 20s would be the most likely candidates to receive it, she said.
The multi-strain cross-protection Cervarix offers is a bonus, Winer added, and "worth investigating further" to see what is behind it.
Another vaccine for cervical cancer, called Gardasil, is also awaiting approval from the U.S. Food and Drug Administration, noted Janet Skidmore, a spokeswoman for the vaccine's developer, Merck. She believes it could be on the market by later this year.
Gardasil protects against HPV 16 and 18, and also against HPV 6 and 11, which Skidmore said accounts for about 90 percent of genital warts.
More information
To learn more about cervical cancer, visit the National Cancer Institute.
