Oct. 15, 2012 -- Adolescent girls who get the human papillomavirus (HPV) vaccine are no more likely to show signs they may be engaging in sexual activity than girls who do not get the vaccine, according to a new study that challenges a widely held belief.
HPV is the most common sexually transmitted virus, and some strains of the virus can lead to oral and genital cancers. The U.S. Centers for Disease Control and Prevention as well as the American Academy of Pediatrics recommend the HPV vaccine for girls and boys as young as age 11.
Previous surveys have found that some parents are concerned their daughter may be more likely to engage in sexual activity if they receive the vaccine.
"Some parents are concerned that saying 'yes' to the HPV vaccine is also encouraging teenagers to say 'yes' to sex," said Dr. Carol Ford, chief of the Craig Dalsimer division of adolescent medicine at the Children's Hospital of Philadelphia.
The new findings, published Monday in the journal Pediatrics, are the first clinical data to study the concern, and found that HPV vaccine does not lead to increased sexual activity among adolescent girls.
Researchers from Emory University in Atlanta followed electronic data of nearly 1,400 girls aged 11 and 12 between July 2006 and December 2010 to see whether they received at least one dose of the vaccine within the first year and whether they were later counseled about contraception, acquired a sexually transmitted disease or became pregnant.
More than a quarter of girls ages 15 to 17 report being sexually active, according to the CDC.
The study followed the girls to the age range where sexual activity would have been initiated, according to the researchers.
The nearly 500 girls who received at least one dose of the vaccine were no more likely to be diagnosed with a sexually transmitted disease, discuss contraception or become pregnant than the nearly 900 girls who did not get the vaccine, the study found.
"We couldn't directly look at sexual activity, so we looked at external outcomes that would suggest sexual activity," said Dr. Robert Bednarczyk, clinical investigator with the Kaiser Permanente Center for Health Research Southeast, and lead author of the study.
The study is based on the assumption that girls who engage in sexual activity would seek care for a sexually transmitted disease, ask for contraception or become pregnant.
According to some experts, the effectiveness and safety of the vaccine are more concerning to many parents than whether their child will see it as a gateway to sexual activity. Still, the findings are reassuring to a smaller group of parents who may see this it as a reason to be apprehensive.
"Those of us who work with adolescents are happy to use this information in discussing the vaccine with parents," said Dr. Eve Shapiro, a pediatrician in Tucson, Ariz.
In previous surveys, adolescent girls reported that they would not be more likely engage in sexual activity if they got the vaccine.
"We did a clinical validation of the self reported data," said Bednarczyk. "This is reassuring to physicians and the parents that the concern doesn't need to be there."
The HPV vaccine does not protect against all strains of the virus or other types of sexual transmitted infections.
Still, adolescent girls should be counseled about the risks of having sex, regardless of whether they have received the vaccine, according to Dr. Linda Reid Chassiakos, director of the Klotz Student Health Center at California State University in Northridge.
"While the HPV vaccine is valuable, the provider needs to be explicit about its specific scope, and should discuss, at the age appropriate time, the risks of unprotected sexual activity," she said.