Real-world Effectiveness of Human Papillomavirus Vaccination Against Cervical Cancer.

Abstract

BACKGROUND\nThe primary goal of human papillomavirus (HPV) vaccination is to reduce morbidity and mortality from HPV-associated disease, especially cervical cancer. We determined the real-world effectiveness of HPV vaccination against cervical cancer.\n\n\nMETHODS\nThe study included women 17-30 years living in Denmark October 2006-December 2019. From nationwide registries, information on HPV vaccination and cervical cancer diagnoses were retrieved. Incidence rate ratios (IRRs) with 95% confidence intervals (CI) for cervical cancer according to vaccination status were estimated using Poisson regression with HPV vaccination treated as a time-varying variable and stratified by age at vaccination. We adjusted for attained age, education, and ethnicity. To address the effect of prevalent disease, different buffer periods were used, with one-year buffer period as primary analysis.\n\n\nRESULTS\nThe cohort comprised 867,689 women. At baseline, 36.3% were vaccinated at\u2009≤\u200916 years, and during follow-up, 19.3% and 2.3% were vaccinated at 17-19 and 20-30 years, respectively. For women vaccinated at\u2009≤\u200916 or 17-19 years, the IRRs of cervical cancer were 0.14 (95% CI:0. 04-0.53) and 0.32 (95% CI: 0.08-1.28), respectively, compared to unvaccinated women. In women 20-30 years at vaccination, the IR was higher than among unvaccinated women (IRR=1.19, 95% CI: 0.80-1.79), but slightly decreased with increasing buffer period (IRR=0.85 (95% CI: 0.55-1.32) with four-year buffer period).\n\n\nCONCLUSION\nHPV vaccine effectiveness against cervical cancer at the population-level is high among girls vaccinated before age 20 years. The lack of immediate effect in women vaccinated at age 20-30 years points to the importance of early age at vaccination.