Young women who get the human papillomavirus (HPV) vaccine don't see it as a license to have more sexual partners or forgo condoms, a new study confirms.
The U.S. Centers for Disease Control and Prevention calls for both girls and boys to be vaccinated against HPV, the sexually transmitted virus that causes cervical cancer.
Some parents have been concerned that the vaccine might promote risky sex, however, and the issue of HPV vaccination became a topic of debate during the 2012 Republican primaries.
But in the new study, even the small group of girls who misunderstood their risk of sexually transmitted infections (STIs) after getting vaccinated didn't change their behavior as a result, researchers found.
"There are so many contributing factors to whether an adolescent decides to have sex or not, and whether they decide to limit their number of partners or use condoms," said Dr. Jessica Kahn. "Getting a vaccine probably just plays a very, very small role in their decisions."
Kahn worked on the study at Cincinnati Children's Hospital Medical Center in Ohio.
Her team's findings are in line with another report that showed girls who had been vaccinated weren't more likely to get other STIs or become pregnant.
"To me, the issue is laid to rest," Kahn told Reuters Health. "As clinicians and researchers, we have no concerns that vaccination will lead to riskier sexual behaviors."
She and her colleagues studied 339 young women between 13 and 21 years old who were getting their first of three HPV shots. Most of the women were black and came from low-income families.
The researchers surveyed participants about how important they considered safe sex to be, and how concerned they were about STIs. Then they asked the participants about changes in their sexual behavior when the young women came back two and six months later for their next shots.
After getting the first vaccine, most young women agreed it was still necessary to use condoms and generally practice safe sex. On a scale from zero to 10, where lower scores indicate a better understanding of risks, participants scored a 1.6, on average.
Most study participants also understood that the HPV vaccine doesn't protect against other STIs, and they scored a 3.9 on their perceptions of STI risks, according to findings published in Pediatrics.
"The vast majority of girls thought that safer sexual behaviors were still important after vaccination," Kahn said. But even those who didn't accurately perceive their risks weren't any more likely to start having sex or stop using condoms, her study showed.
Among women who said they had never had sex when they got their first vaccine, 20 percent had become sexually active by the time the researchers checked in with them six months later.
Of those who were already having sex when the study started, close to two thirds said at their six-month visit that they used a condom the last time they had sex. About one third reported two or more sexual partners since their last visit.
"The findings strengthen a growing body of literature that indicates that getting HPV vaccination is very unlikely to change an adolescent's perception about risk and also their actual sexual behavior," Dr. Amanda Dempsey said.
Dempsey is a pediatrician and vaccine researcher at the University of Colorado, Denver and wasn't involved in the new research. She tells parents that young people's attitudes on sex are based on years of discussions about family values - so a shot shouldn't have a major effect.
Kahn said she is worried that parents' concerns about changes in sexual behavior might still be keeping them from getting their children vaccinated.
HPV vaccination rates are relatively low. One in three girls between 13 and 17 years old had gotten all three shots in 2012, the researchers noted.
But vaccination has been shown to be safe and to prevent pre-cancers, Kahn said.
"It's just so important for us to try to get vaccination rates to increase so we can protect young women and young men against these infections and prevent cancer in the future," she said.
Two of the study's seven authors have received grants from the two companies that sell HPV vaccines, Merck and GlaxoSmithKline. The current study was funded by the U.S. National Institutes of Health.