UCSF doctors warn on wide use of cervical cancer vaccine
They urge caution while clinical trials are still under way
Erin Allday, Chronicle Staff Writer
Thursday, May 10, 2007
Nearly a year after a controversial cervical cancer vaccine won federal approval and hit the market to a whirlwind of interest from doctors and parents, at least two UCSF physicians are warning against widespread use of the drug until much more extensive studies are complete.
In an editorial published in today's New England Journal of Medicine, the UCSF doctors suggest that there are still too many questions about both the efficacy and the long-term safety of the vaccine, called Gardasil, to warrant making it mandatory for all girls -- as has been suggested in several states, including California.
"At this stage, vaccination can still be considered experimental," said Dr. Karen McCune, an associate professor of obstetrics and gynecology at UCSF, who co-authored the editorial. "To be discussing mandatory vaccination when the main clinical trials are still ongoing seems extremely premature. We're feeling like the enthusiasm is driving policy rather than data."
The cervical cancer vaccine, manufactured by Merck & Co., was approved by the Food and Drug Administration in June 2006 and became widely available last fall. The vaccine is designed to prevent infection from the sexually transmitted human papilloma virus that causes cervical cancer. The same virus also increases the risk of developing other cancers -- including throat cancer, according to a study also released today in the New England Journal of Medicine.
The vaccine, to be most effective, should be given to girls before they have sex and may be exposed to the virus that causes cancer. Researchers are hoping that the vaccine also may prove effective at preventing other cancers, although there have yet to be any thorough studies addressing the possibility.
Cervical cancer is the second-most common cancer among women worldwide and the third-most fatal, causing 290,000 deaths a year. The disease is rare in the United States, where regular screening for adult women catches most precancerous cases; about 3,700 American women die of cervical cancer every year.
Shortly after the vaccine won FDA approval, a federal advisory panel recommended that all 11- and 12-year-old girls be vaccinated. Since then, several states have considered proposals making vaccination mandatory for girls.
A bill in the California Legislature requiring vaccination stalled in committee in March over concerns about parental rights and the lack of information about the long-term effects of the vaccine. The author has amended his bill to address the wider issue of how California requires vaccinations. In Texas, Gov. Rick Perry backed off this week from orders to force all sixth-grade girls in the state to be vaccinated.
In clinical trials, the vaccine has proved very effective at preventing infection from two strains of HPV that cause 70 percent of cervical cancer cases. Researchers released new data today -- also published in the New England Journal of Medicine -- based on a study of 15,000 women, that showed the vaccine was about 98 percent effective in preventing infection of the two HPV strains.
"Certainly, (the published data) should give the lay public and the professional groups proof that this vaccine is very effective," said Dr. Kevin Ault, a professor of obstetrics and gynecology at Emory University School of Medicine and one of the study's authors.
But the primary concerns of doctors like McCune are that long-term side effects of the vaccine are unknown -- the most recent study followed women for three years -- and that earlier research hasn't considered what effect the vaccine has on the remaining 13 strains of HPV that also cause cervical cancer.
It's possible, McCune said, that the remaining strains may fill a "niche" left if the two most common strains are wiped out entirely. If that happens, the vaccine might not make any difference on overall cervical cancer rates, she said.
But while many doctors agree that there are still questions about the vaccine, they note that there is no question that Gardasil is effective at stopping the most common cancer-causing HPV strains. And because the vaccine is most effective before a woman has had sex, it's important that girls get vaccinated as soon as possible, even if some doubts remain, some doctors say.
E-mail Erin Allday at [email protected]