|Page 2 of 2 <|
Millions In U.S. Infected With HPV
Most of the time a woman's immune system clears the virus within weeks, although repeated reinfections are possible. In some cases, however, the virus becomes incorporated in cervical cells and can cause malignant changes.
Cervical cancer was once the leading cause of cancer death in American women. Routine screening with Pap smears has reduced deaths dramatically in the last three decades. Last year, there were about 9,700 new cases of cervical cancer in the United States and 3,700 deaths. About 85 percent of the women who died had never had a Pap smear.
Worldwide, cervical cancer is responsible for about 235,000 deaths a year, but only 17,000 occur in industrialized countries.
In the 2003-2004 round of the national health survey, about 2,000 females aged 14 to 59 submitted self-collected vaginal swabs. Laboratory testing detected HPV in 27 percent of them. In the 14-to-24 age group, the rate was 34 percent. The highest prevalence -- 45 percent -- was in women age 20 to 24.
HPV also infects boys and men, in whom it can cause genital warts and anal cancer. Males were not tested in the survey, although researchers are trying to come up with ways to do that, Dunne said.
An earlier study of college students found that more than 50 percent acquired HPV within four years of first sexual intercourse. In the new survey, HPV infection was more likely in women under age 25, in unmarried women, and in women with two or more partners, especially in the year before testing.
The Merck vaccine is a three-shot course costing about $360. The committee that advises CDC on vaccine policy recommended its routine use in 11- and 12-year-old girls to protect them against the four strains before they become sexually active.
Although infection produces antibodies, they do not appear to prevent future reinfection, said Lawrence R. Stanberry, a vaccine researcher at the University of Texas Medical Branch in Galveston.
"This is a situation where the vaccine really looks like it provides much better immunity than what you would get if you allowed yourself to become naturally infected," he said.
Whether the immunity will last a lifetime is uncertain. Preliminary evidence suggests it may start to dwindle after five years. A vaccine being developed by GlaxoSmithKline, which targets only HPV-16 and HPV-18, contains an antibody-boosting "adjuvant" that may provide longer-lasting immunity.
Merck, which sells its product under the trade name Gardasil, has been lobbying for laws requiring the vaccine for schoolgirls. After criticism from politicians and editorial writers, it recently said it will stop doing so.