Human papillomavirus (HPV) vaccination has been reimbursed in Belgium since 2007 for girls (12-15 years), extended to girls up to 18 years in 2008. This study assesses the trend of HPV 16/18 infections in women less than 25 years of age participating in opportunistic cervical cancer screening. A significant reduction in the prevalence of HPV 16 [relative risk (RR)=0.61, 95% confidence interval=0.39-0.95] and a nonsignificant reduction in HPV 18 (RR=0.65, 95% confidence interval=0.29-1.48) was found in the youngest group (15-19 years). The prevalences in the older age group did not change significantly. These findings show the early effects of HPV vaccination and confirm the effectiveness of immunization in a real-life setting.