The finding that early sexual activity is not predictive of future HPV infection suggests that using risk factors as a means of determining who should get vaccinated against HPV is not an effective strategy, researcher Amanda F. Dempsey, MD, PhD, of the University of Michigan tells WebMD.
Most women become infected with at least one of the more than 100 HPV types soon after becoming sexually active, but the infection usually clears up on its own. When infection persists it can lead to cervical cancer and genital warts.
The HPV vaccine targets two HPV types that cause roughly 70% of cervical cancers and two other types responsible for almost all genital warts.
"In our study, all women who eventually became sexually active at some point had an equivalent risk of getting HPV," Dempsey says.
HPV Vaccine Strategy
The HPV vaccine has been widely available for a little over a year. The CDC and the American Cancer Society agree that all girls between the ages of 11 and 12 should get the three-shot vaccination series.
But while CDC recommends vaccinating all women up to age 26 regardless of sexual history, the American Cancer Society recommends vaccinating all women younger than 18 and selectively vaccinating those between the ages of 19 and 26, based on sexual history.
The more sexual partners someone has had, the less likely the vaccine will be effective for lowering cervical cancer risk.
This and the fact that the vaccination series can cost uninsured women as much as $1,000 led to the recommendation, American Cancer Society Director of Breast and Cervical Cancer Debbie Saslow, PhD, tells WebMD.
"We never make recommendations based on cost alone, but we do consider cost-effectiveness," she says. "The vaccine just isn't cost-effective from a cancer standpoint for a woman in her 20s who has five or 10 sexual partners."
HPV Risk Examined
Dempsey counters that it is unlikely that a sexually active woman has been exposed to all four HPV types that the vaccine protects against, so denying her the vaccine based on her sexual past could jeopardize her health.
"Few studies have evaluated the ability of specific risk factors to predict future HPV infection prospectively," Dempsey and colleagues write in the July issue of Pediatrics. "This is an important distinction, given that HPV vaccines must be provided before vaccine type-specific infection to be effective."
In an effort to determine the value of adolescent risk factors for predicting future HPV infection, Dempsey and colleagues examined data on more than 3,000 women who had participated in a nationwide study of adolescent health.
The girls were in middle school and high school when they were enrolled in the study; the analysis included health evaluations and surveys conducted over a six-year period.
Researchers selected six behaviors suggestive of a higher HPV risk in previous studies: number of sexual partners; having had an older male sexual partner and/or a new partner within the past year; illegal drug use; regular use of alcohol or cigarettes; and having sex while under the influence of alcohol.
Nearly half (43%) of the young women were sexually active when they entered the study between the ages of 13 and 18.
Six years later there was little difference seen in HPV infection based on the early risk factors.
Fifty-three percent of the participants who tested positive for HPV six years after entering the study were not yet sexually active when first surveyed.
"This underscores the fact that HPV is very common in our society and you don't have to do anything outside the realm of what is considered nonrisky sexual behavior to acquire it," Depsey says. "That is why the HPV should to be given to everyone who is eligible."
But Saslow says this would place a big burden on low-income young women who may derive little benefit if they have been sexually active for many years. The Federal Entitlement Vaccine Program covers the cost of the vaccine series for women who are 18 and under, but not for older women.
"You are talking about an awful lot of low-income women between the ages of 19 and 26 who would be asked to pay anywhere from $500 to $1,000 out of pocket," she says.
By Salynn Boyles
Reviewed by Louise Chang
©2005-2008 WebMD, LLC. All rights reserved