Photograph of Dr. Noel T. Brewer

A second study, led by the same researcher, shows that only six to 12 percent of parents are concerned that vaccinating their children against HPV will encourage them to have more sex. The studies were published June 2007 in the Annals of Behavioral Medicine and Preventive Medicine. 

Noel T. Brewer, PhD, assistant professor of health behavior and health education at the UNC School of Public Health and lead investigator of both studies, said that while there is a small chance that getting vaccinated for HPV may lead adolescent girls to engage in behaviors that expose them to levels of risk similar to those experienced by unvaccinated girls, it will not lead them to engage in behaviors that expose them to higher levels of risk.

"One of the main arguments against vaccinating young women for HPV is that they will somehow compensate for the vaccine's protective nature by having more sex, to the point that their overall risk for sexually transmitted diseases becomes higher than before they were vaccinated," said Brewer. "Our findings say otherwise."

In the last two years, the Food and Drug Administration has approved the HPV vaccine Gardasil for use in females, 9 to 26 years old. Eighteen states are now considering making HPV vaccination mandatory for young girls entering middle or high schools. However, some groups have publicly opposed mandatory inoculation, claiming it might encourage more young women to engage in premarital sex.

To understand how the HPV vaccine may affect sexual behavior, Brewer, James E. Herrington, PhD, director of the Division of International Relations at the National Institutes of Health, Cara L. Cuite, research project manager at the Cook Food Policy Institute at Rutgers University, and Neil D. Weinstein, emeritus professor of human ecology at Rutgers University, studied Lyme disease vaccination behaviors shortly after the Lyme disease vaccine first became available to the public. Brewer said that in the absence of an actual behavioral study using the HPV vaccine, the Lyme disease vaccine is a strong test of how risk perception affects behavior, because it was also a brand new vaccine at the time of testing. 

The researchers asked a random sample of 705 adults in northeastern U.S. areas with high Lyme disease incidence what protective behaviors they engaged in, such as using tick repellent, wearing light colored clothing and avoiding certain areas of their yards, before and after they were vaccinated. They found that vaccinated respondents were less likely to continue using one of five protective measures after vaccination, but the frequency of those measures did not dip below that among unvaccinated respondents.

"We found no evidence of disinhibition, where people started taking greater risks than the general population," Brewer said.

Study authors added that it is unlikely adolescent girls will overcompensate for HPV vaccination by having more sex because most of them don't even associate cervical cancer and HPV with sex.

"People have to believe that sex is connected to HPV and cervical cancer," said Brewer. "But several studies show that these beliefs don't exist for most women. If adolescent girls don't connect cervical cancer to sex, they are unlikely to believe that HPV vaccination will lessen their risk of getting cervical cancer through sex -- a belief that might encourage them to go ahead and have more sex."   

Meanwhile, a literature review of 28 studies on predictors of HPV vaccine acceptability, conducted by Brewer and Karah I. Fazekas, a UNC School of Public Health graduate, shows that only six to 12 percent of parents are concerned that their children will have more sex once they are vaccinated.

"For parents, more important considerations for wanting to get the HPV vaccine are a doctor's recommendation, feeling at risk for cervical cancer, and believing that the vaccine is safe and effective," said Brewer. "Most Americans think adolescent girls should get the vaccine."

Brewer said that the findings of the two studies should free policymakers from concerns that their constituents would oppose adopting the HPV vaccine, or that mandating the vaccine would actually lead to more risky sexual behaviors among adolescents. Instead, health officials should focus on ensuring HPV vaccine uptake in high-risk women who need the vaccine most.

Risk factors for cervical cancer include race, income and social status. Minorities, indigents, people who live in rural areas, women who live in developing countries, and smokers are all considered high-risk groups.

Note: Brewer can be reached at (919) 843-7896 or ntba@unc.edu.

Web site: http://www.cdc.gov/std/hpv/STDFact-HPV-vaccine.htm.

School of Public Health contact: Ramona DuBose, director of communications, (919) 966-7467 or ramona_dubose@unc.edu.

News Services contact: Becky Oskin, (919) 962-8596 or becky_oskin@unc.edu.