Article Print

It may be another year or two before a vaccine for cervical cancer is available, but pediatricians are already expressing an interest in providing it to adolescents who are not yet sexually active. The vaccine works by preventing infection with the human papillomavirus (HPV), a common sexually transmitted disease (STD) that causes most cases of cervical cancer.

Excitement for the vaccine has been building since researchers announced that one early version, called Gardasil, was 100 percent effective in blocking HPV infection. But the vaccine raises a difficult issue for parents. Would inoculating adolescents against an STD promote unsafe sex?

This question will need to be answered soon. If the dramatic results hold up in further testing, the HPV vaccine may be available as early as 2006. In the meantime, researchers took pause to rejoice in the recent good news.

"There's almost nothing that's 100 percent in medicine," says study author Dr. Kevin Ault, assistant professor of obstetrics and gynecology at Emory University School of Medicine. "It's pretty exciting."

The End of Cervical Cancer?
Dr. Eliav Barr, senior director of Clinical Research at Merck Research Laboratories, explained that Gardasil was designed to target the two types of HPV most commonly associated with cervical cancer, as well as the types that cause genital warts and many abnormal Pap smears. Barr said his hope was "to reduce the burden from HPV-related diseases as much as possible."

The study on Gardasil, presented at a meeting of the Infectious Diseases Society of America this October, included an international group of over 12,000 sexually active women between the ages of 16 and 26. Half received three doses of the HPV vaccine, and the other half received placebo shots.

After seven months, those who were virus-free were followed for an additional 17 months. In this group, none of the women who were vaccinated developed either cervical cancer or precancerous lesions in their cervix, while 21 of the women in the placebo group did. This shows that the vaccine is 100 percent effective when all doses are administered before a woman contracts HPV.

In a follow-up, the researchers expanded their analysis to include all women who were virus free after only the first dose of the vaccine. This left room for those who may have contracted HPV before the end of the vaccination cycle to be included in the final tally—making the results more realistic, according to the researchers.

In this later analysis, only one woman in the vaccinated group was found to have precancerous growths, while 36 of the unvaccinated women had developed either precancerous growths or cervical cancer. In this more "real world" sample, the risk of developing precancerous growths was reduced by 97 percent after taking Gardasil.

"These results show that even if you got infected while receiving the vaccine, you were protected [against cervical cancer]," explains Ault.

Preventing a Killer
Cervical cancer was once the most common cause of cancer death for American women. But the increased use of Pap screening has helped to reduce the death rate by 75 percent, as the test can detect precancerous changes in the lining of the cervix at a stage where the cancer is most curable. Still, it is estimated that over 10,000 cases of cervical cancer will be diagnosed this year, resulting in over 3,000 deaths

Any sexually active woman who has sexual contact with an infected partner is at risk for acquiring HPV, no matter how much protection is used. Even routine condom use does not decrease this risk, as the virus is spread through either through contact with the skin or mucous membranes of an infected partner. An HPV infection may cause visible genital warts, but an infection may be present even without such warning signs.

As there are over 100 strains of the HPV virus and only a few are known to be cancerous, most cases of HPV will never develop into cervical cancer. In fact, infections generally clear up by themselves, according to Laurie Markowitz, a medical epidemiologist for the Centers for Disease Control.

Because HPV may go unnoticed for several years, the American Cancer Society recommends that all women begin getting annual Pap smears as soon as they become sexually active, but no later than 21 years of age. If three normal Pap smears have been taken by the time a woman is 30, she may go three years between tests.

The Vaccine in Practice
Even if Gardasil is approved, a woman who is vaccinated against HPV would still need routine Pap smears, says Ault. Since the vaccine only eliminates the biggest cause of cervical cancers, other cases are still possible. "But you would expect a huge decrease in the number of abnormal Pap smears," predicts Ault.

Although some questions remain as to how popular a vaccine against a sexually transmitted disease will be, a study published in September 2005 in the Journal of Adolescent Health showed that up to 80 percent of parents were in favor of having their child vaccinated against treatable sexually transmitted infections, like HPV. (90 percent were in favor of vaccinations against HIV and herpes, STDs that have no cure). And in a recent survey, only 11 percent of doctors felt that immunizing against the virus would encourage promiscuous sexual behavior.

But because HPV is so closely tied to cervical cancer, Ault feels that those who "make the connection between HPV and cervical cancer," would be more likely to approve of the vaccine for their children, as then the infection would be perceived as "more serious."

"Parents want to protect their children against harm," said Ault.