February 11, 2015 — Girls do not begin engaging in riskier sexual behavior after they receive the human papillomavirus vaccine, according to a study published Monday in JAMA Internal Medicine, the Washington Post's "To Your Health" reports.
For the study, researchers from Harvard University and the University of Southern California examined insurance claims for girls ages 12 to 18 who were enrolled in 50 health plans throughout the U.S. The researchers compared the rates of chlamydia, gonorrhea, herpes, HIV/AIDS and syphilis among 21,000 girls who received the HPV vaccine and more than 186,000 girls who did not (Izadi, "To Your Health," Washington Post, 2/9).
According to HealthDay/U.S. News & World Report, the researchers based the study on the premise that STI diagnoses would increase in the year after vaccination if the HPV vaccine was associated with increased risky sexual behaviors (Norton, HealthDay/U.S. News & World Report, 2/9).
The study found that STI rates among vaccinated girls were higher both before and after vaccination, compared with unvaccinated girls ("To Your Health," Washington Post, 2/9). Specifically, the rate of vaccinated girls with an STI diagnosis was 1.6 cases per 1,000 girls in the year before vaccination, compared with 0.9 per 1,000 for the unvaccinated group. In the year after vaccination, the rates in the vaccinated and unvaccinated groups increased to 2.4 per 1,000 and 1.4 per 1,000, respectively (Kaplan, Los Angeles Times, 2/9).
Researchers also compared the rate of change in STI diagnoses for the groups to assess whether vaccination was associated with changes in sexual behavior, but their analysis found no indication that sexual activity increased after vaccination, according to study author and Harvard Medical School assistant professor Anupam Jena ("To Your Health," Washington Post, 2/9). However, the study noted that risk of contracting an STI seemed to increase with age.
The researchers wrote that the "findings should be reassuring to physicians, parents, and policy makers that HPV vaccination is unlikely to promote unsafe sexual activity" (Los Angeles Times, 2/9).
Jena noted, "The vast majority of parents" do not believe that HPV vaccination is tied to increased promiscuity, "[b]ut 10 to 20 percent of parents and at least some pediatricians think that this could be an issue." Jena said he hopes the study's results will quash some of those concerns (Doyle, Reuters, 2/9).
Meanwhile, Emory University epidemiologist Robert Bednarczyk wrote in a commentary accompanying the study that he hopes the findings will help to reduce "the stigma of HPV vaccine" in the U.S., where HPV vaccination rates are relatively low. He continued, "Just as we do not wait until we have been in the sun for two hours to apply sunscreen, we should not wait until after an individual is sexually active to attempt to prevent HPV infection" (Los Angeles Times, 2/9).