Objective: Previous surveys on hypothesized sexual activity changes after human papillomavirus (HPV) vaccination may be subject to self-response biases. To date, no studies measured clinical markers of sexual activity after HPV vaccination. This study evaluated sexual activity-related clinical outcomes after adolescent vaccination.
Methods: We conducted a retrospective cohort study utilizing longitudinal electronic data from a large managed care organization. Girls enrolled in the managed care organization, aged 11 through 12 years between July 2006 and December 2007, were classified by adolescent vaccine (HPV; tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis, adsorbed; quadrivalent meningococcal conjugate) receipt. Outcomes (pregnancy/sexually transmitted infection testing or diagnosis; contraceptive counseling) were assessed through December 31, 2010, providing up to 3 years of follow-up. Incidence rate ratios comparing vaccination categories were estimated with multivariate Poisson regression, adjusting for health care-seeking behavior and demographic characteristics.
Results: The cohort included 1398 girls (493 HPV vaccine-exposed; 905 HPV vaccine-unexposed). Risk of the composite outcome (any pregnancy/sexually transmitted infection testing or diagnosis or contraceptive counseling) was not significantly elevated in HPV vaccine-exposed girls relative to HPV vaccine-unexposed girls (adjusted incidence rate ratio: 1.29, 95% confidence interval [CI]: 0.92 to 1.80; incidence rate difference: 1.6/100 person-years; 95% CI: -0.03 to 3.24). Incidence rate difference for Chlamydia infection (0.06/100 person-years [95% CI: -0.30 to 0.18]) and pregnancy diagnoses (0.07/100 person-years [95% CI: -0.20 to 0.35]), indicating little clinically meaningful absolute risk differences.
Conclusions: HPV vaccination in the recommended ages was not associated with increased sexual activity-related outcome rates.