Seattle- Researchers at the University of Washington have demonstrated for the first time that condoms can prevent women from becoming infected with the human papillomavirus, a common sexually transmitted disease that can lead to cervical cancer.

More than half of all sexually active men and women will contract HPV at some point in their lives, according to the Centers for Disease Control and Prevention.

Previous studies could not conclude that condoms helped protect against HPV, a lack of evidence conservatives have used in support of abstinence as the only 100 percent effective method for preventing the transmission of disease.

In the UW study, women whose partners used a condom every time they had sex were 70 percent less likely to contract HPV than those whose partners used a condom less than 5 percent of the time.

Scientists asked 82 students, ages 18 to 22, at the UW to record their sexual behavior on an electronic diary every two weeks between December 2000 and June 2005.

“It really shows the right way to study condom effectiveness,” said Dr. Hunter Handsfield, an STD expert and former director of the STD Control Program at Public Health — Seattle & King County.

To avoid recruiting women who’d been infected before the study’s outset, researchers at the UW enrolled only women who’d never had sex.

Handsfield praised the study’s design for asking women about condom use before they had contracted HPV, rather than relying on memory months after a diagnosis.

The UW study, published today in the New England Journal of Medicine, comes on the heels of the Food and Drug Administration’s approval earlier this month of Gardasil, a vaccine for cervical cancer.

The vaccine protects against two strains of HPV that cause 70 percent of cervical cancer and two other strains that cause 90 percent of genital warts. Some conservatives have balked at adding Gardasil to the battery of vaccines already required for school attendance, suggesting that young girls may consider it a license to have sex.

Some conservative groups also have argued that, in the absence of strong evidence, condoms should carry labels warning they do not protect against HPV and other STDs.

Since 2001, the Food and Drug Administration has been considering revisions to condom labels.

The UW study created a buzz among experts when it was first presented at the International Society for Sexually Transmitted Research in July, Handsfield said.

“This study, from a political and social policy perspective, is probably the most important research in STDs in the last five years,” Handsfield said.

The authors of an editorial also published in the New England Journal this week, said the UW study, along with other recent studies, offer more clarity about the relationship between STDs and condoms.

Other recent studies have indicated that condoms reduce the risk of gonorrhea, chlamydia and herpes. Using a condom cuts the risk of HIV transmission by 80 to 90 percent, according to the editorial.

“Strong empirical evidence indicates that condom use considerably reduces the risk of transmission of most sexually transmitted infections,” wrote Dr. Markus Steiner and Dr. Willard Cates Jr. from the Institute for Family Health at Family Health International.

HPV is spread during sex from contact with the sores, or lesions, that develop around infected cells.

That means, unlike other STDs including HIV, HPV can be transmitted by skin-to-skin contact, said Rachel Winer, an epidemiologist at the UW and lead author of the study.

“Obviously, (condoms weren’t) 100 percent effective” in the study, Winer said. “Even if you use a condom properly, there might be areas of genital skin that aren’t covered.”

Often, the virus is killed by the immune system, but in some people HPV can take hold and cause lesions that can turn cancerous years later. Cervical cancer strikes about 10,520 American women and kills about 3,500 each year. Worldwide, about 500,000 women develop cervical cancer and nearly 300,000 die from it every year.

“This is about as ideal a study as you can get,” said Dr. Tom Fitch, a San Antonio pediatrician and board chairman at the Medical Institute for Sexual Health, which stresses abstinence and monogamy as the only sure ways to prevent sexually transmitted infections.

Fitch noted that some consistent condom users still were infected with HPV. Fitch also suggested that the results in the real world — say, among poor, inner-city women — might be different from those with college women.

Fitch said several studies have shown that at most, 50 percent of people reported using a condom every time they had sex.

Neither the new vaccine or condoms can protect women entirely from cervical cancer, said Winer.

“It’s important that women keep getting screened regularly for cervical cancer.”