Vaccine Blocks Most Cancers of the Cervix
An experimental vaccine against cervical cancer has cleared its final clinical hurdle, showing in a large trial of more than 12,000 women that it is 100% effective in blocking the major forms of the disease, its manufacturer said Thursday.
Merck Inc. said it would seek Food and Drug Administration approval for the vaccine, called Gardasil, this year and could begin marketing it next year. The vaccine immunizes against human papilloma virus, or HPV, the primary cause of cervical cancer.
If approved, the vaccine would probably be administered to children 12 or younger, before they become sexually active -- including boys, who can be carriers of the virus.
The vaccine protects against a virus that has infected 20 million Americans and prevents a cancer that kills 3,900 American women each year. There is no treatment for HPV.
Cervical cancer death rates are low in the U.S. because of widespread Pap screening, but worldwide, cervical cancer is the second-leading form of fatal cancer in women, killing about 250,000 a year.
“This is a tremendous breakthrough,” said Dr. David A. Fishman, a gynecologic cancer specialist at the New York University School of Medicine. “This is needed globally to reduce the high incidence of cervical cancer.”
Researchers reported last year that an early version of the vaccine prevented cancer in a trial involving about 1,500 women.
The new study, to be presented this evening at a San Francisco meeting of the Infectious Diseases Society of America, used a more sophisticated vaccine that is targeted against four strains of HPV instead of one.
Researchers have identified 20 strains of human papilloma viruses since the discovery of HPV about 20 years ago. Five of them cause cervical cancer.
The primary treatment for cervical cancer is a hysterectomy, which has a 92% cure rate if the cancer is caught early.
The original vaccine targeted HPV-16, which causes about half of cervical cancers. Gardasil also prevents HPV-18, which causes 20% of cervical cancers.
Researchers have previously reported that the vaccine is 95% to 97% effective in blocking infections by the two strains.
Gardasil also produces immunity against two other viruses, HPV-6 and HPV-11, which cause about 90% of genital warts. The researchers have not yet released information about the effectiveness against warts.
The researchers, led by Dr. Laura A. Koutsky of the University of Washington in Seattle, enrolled 12,167 women, ages 16 to 26, in 13 countries. None had HPV-16 or HPV-18.
Half received a three-dose vaccine regimen over a six-month period; the rest received a placebo. The researchers detected no significant side effects.
Because cervical cancer takes years to develop, the researchers looked for abnormalities in the cervix called precancerous lesions, which almost always progress to cancers if left untreated.
In the two years of the study, no one who received all three doses had precancerous lesions associated with HPV-16 or 18 -- a 100%-effective rate. In the placebo group, 21 women had precancerous lesions.
Among the women who did not receive all three doses of vaccine or who did not follow the study protocol completely -- they may have taken prescription drugs, such as steroids, that interfere with immunization, for example -- the efficacy fell to 97%.
That’s still very effective, said Dr. Kevin Ault of Emory University, one of the study’s authors, and “it approaches real-world conditions,” where not everyone comes back for all her shots.
Gardasil is one of two HPV vaccines being tested. GlaxoSmithKline Biologicals’ version, Cervarix, targets HPV-16 and 18.
Cervarix proved 100% effective in early trials; GlaxoSmithKline is still enrolling women in the trials testing it against cervical cancer. The company is expected to release results from that trial next year and to begin marketing the vaccine in 2007.
Both vaccines were developed by Dr. Douglas Lowy of the National Cancer Institute. They are made of virus-like particles, grown in yeast, that contain all the surface proteins of the viruses but none of their genetic information. The proteins stimulate immunity to the viruses.
The institute granted rights to the vaccines to the two companies.
The vaccine has raised some concerns that vaccinating children against a sexually transmitted disease could inadvertently be perceived as endorsing promiscuity.
“This has the potential to be a wonderful medication that is going to prevent a lot of heartbreak, but I do have a concern about the message we send,” said Dr. Hal Wallis, director of the conservative Physicians Consortium, which advises Focus on the Family and other religious groups about medical issues.
“I have mixed emotions about it,” he said.
When the vaccines are ultimately marketed, Wallis said, they will have to be presented carefully. If young girls think they can get a shot and somehow be protected against sexually transmitted diseases, that will be very dangerous, he said.
The vaccine protects “against a very narrow and specific range of STDs,” he concluded, “but that is going to be a hard message to get people to understand.”