The early impact of human papillomavirus vaccination on anogenital warts in Québec, Canada.

In Québec province in Canada, a public school-based and catch-up HPV vaccination programs with the quadrivalent vaccine have been introduced in September 2008 for girls aged 9-17 years. We assessed the early impact of the HPV vaccination program on the incidence of anogenital warts (AGW) in the Quebec general population. We used the provincial health administrative data of the Régie de l'assurance maladie du Québec (RAMQ). AGW were identified either through a prescription of podofilox, or a medical procedure code specific to AGW, or a diagnostic code for viral warts followed by a prescription of imiquimod or fluorouracil. Sex- and age-specific incidence rates were calculated for pre-vaccination (2004-2007) and vaccination (2009-2012) periods. We found a significant decline of 45% and 19% in the incidence of AGWs among females aged 15-19 and 20-24 years, respectively. A decline of 21% was also seen among males aged 15-19 years. The median age at an episode of AGW increased from 27 years in 2004 to 31 years in 2012 among females and remained stable in males. Our findings indicate that the HPV public vaccination program is associated with an important reduction in the incidence of AGW among young females and males. The benefit is more pronounced among females 15-19 years of age, who were eligible for the public vaccination program. The observed decline among young males could be due to herd immunity and/or privately paid vaccination.