Abstract
BACKGROUND: Human papillomavirus (HPV) vaccine effectiveness and herd protection are not well established in community settings. Our objective was to determine trends in vaccine-type HPV in young women during the 8 years after vaccine introduction, to assess changes in HPV prevalence and characterize herd protection in a community. METHODS: We recruited 3 samples of sexually experienced, 13-26-year-old adolescent girls and young women (hereafter women; N = 1180) from 2006-2014: before widespread vaccine introduction (wave 1) and 3 (wave 2) and 7 (wave 3) years after vaccine introduction. We determined the prevalence of vaccine-type HPV (HPV-6, -11, -16, and -18) among all, vaccinated, and unvaccinated women at waves 1, 2, and 3, adjusted for differences in participant characteristics, then examined whether changes in HPV prevalence were significant using inverse propensity score-weighted logistic regression. RESULTS: Vaccination rates increased from 0% to 71.3% across the 3 waves. Adjusted vaccine-type HPV prevalence changed from 34.8% to 8.7% (75.0% decline) in all women, from 34.9% to 3.2% (90.8% decline) in vaccinated women, and from 32.5% to 22.0% (32.3% decline) in unvaccinated women. Among vaccinated participants, vaccine-type HPV prevalence decreased significantly from wave 1 to wave 2 (adjusted odds ratio, 0.21; 95% confidence interval, .13-.34) and from wave 1 to wave 3 (0.06; .03-.13). The same decreases were also significant among unvaccinated participants (adjusted odds ratios, 0.44; [95% confidence interval, .27-.71] and 0.59; [.35-.98], respectively). CONCLUSIONS: The prevalence of vaccine-type HPV decreased >90% in vaccinated women, demonstrating high effectiveness in a community setting, and >30% in unvaccinated women, providing evidence of herd protection.