HealthDay News — Sexual behaviors among adolescent girls vaccinated with human papillomavirus (HPV) vaccine and their unvaccinated peers does not differ, research suggests.

There were no differences among the two groups in pregnancy rates, testing for or diagnosis of sexually transmitted infections, or receipt of contraceptive counseling by a physician among girls aged 11 to 12 years enrolled in a large, managed-care organization, Robert Bednarczyk, PhD, of Kaiser Permanente Center for Health Research-Southeast in Atlanta, and colleagues reported in Pediatrics.

Furthermore, average age at the first composite outcome was no different between vaccinated and unvaccinated girls (14.4 vs. 14.6, P=0.325), suggesting that there may not be earlier onset of sexual activity after HPV vaccination among those who receive the vaccine at the recommended ages.

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“If HPV vaccination was ‘a license for sex,’ we would have expected to see more adverse outcomes shortly after vaccination, when the girls were more aware of their recent vaccination status,” the researchers wrote.

Although the Advisory Committee on Immunization Practices recommended in 2006 that all girls aged 11 to 12 years receive the HPV vaccine in efforts to confer immunity before sexual activity is initiated, HPV vaccine uptake is lower than rates for other recommended adolescent vaccines. Some think concern that vaccinated girls will become sexually active earlier, due to less fear of the disease, may be contributing to these lower rates.

To further explore this idea, Robert A. Bednarczyk, PhD, from Kaiser Permanente in Atlanta, and colleagues examined sexual activity-related clinical outcomes after HPV vaccination in a cohort of 1,398 11- to 12-year-old girls who were enrolled in the organization’s health plan from July 2006 through December 2007.

A total of 493 received HPV vaccine and 905 did not — 35% received at least one dose of HPV vaccine in addition to other vaccines, and the rest received tetanus toxoid, reduced diphtheria toxoid and acellular pertussis (Tdap) vaccine, quadrivalent meningococcal conjugate vaccine (MCV4), or both, but not HPV vaccine. Outcomes were assessed during up to three years of follow-up.

Pregnancy rates, testing for or diagnosis of a sexually transmitted infection, and receipt of contraceptive counseling was 5.5 per 100 person-years in the vaccinated group and 3.9 per 100 person-years in the control group — a difference that was not statistically significant after adjusting for healthcare-seeking behavior, age at vaccination, race and socioeconomic status (incidence rate ratio=1.29; 95% C: 0.92-1.80).

There were also no clinically significant differences in absolute risk for chlamydia infection or pregnancy diagnoses for vaccinated vs. unvaccinated girls, the researchers found.


  1. Bednarczyk R et al. Pediatrics. 2012; doi: 10.1542/peds.2012-1516.