Impact of a single-age cohort human papillomavirus vaccination strategy in Catalonia, Spain: Population-based analysis of anogenital warts in men and women.

Extensive multiple-age cohort human papillomavirus (HPV) vaccination has proved to be highly effective. We aimed to determine the 8-year population impact of a female single-age cohort HPV vaccination programme on the incidence of anogenital warts (AGW). In 2008, Catalonia initiated a school-based quadrivalent HPV vaccination programme targeting 11-year-old girls, achieving coverage over 80%. Data on diagnoses of AGW and genital herpes were obtained from a population-based database of electronic health records covering 74% of the population. The annual incidence rates from 2009 to 2016 were calculated, stratified by age and sex using Joinpoint regression to estimate trends and annual percentage changes (APC). Among women aged 16-19 years, the AGW incidence decreased by 61% from 2012 to 2016 (APC -19.4%; 95% CI: -30.0 to -7.3). In contrast, the incidence of genital herpes in same-aged women increased throughout the study period (APC 11.1%; 95% CI: 7.2-15.2). Among men aged 20-22 years, the increasing incidence of AGW shifted to a downward trend in 2013 (APC 2009-2013: 17.0%; 95% CI: 8.2-26.5; and APC 2013-2016: -4.5%; 95% CI: -14.6 to 6.9). A similar pattern was observed among men aged 23-25 years (APC 2009-2014: 16.0%; 95% CI: 12.0-20.2; and APC 2014-2016: -6.0%; 95% CI: -18.4 to 8.3). In contrast to AGW, among men aged 20-25 years, the incidence of genital herpes increased over this period. Our study strongly suggests that a single-cohort HPV vaccination strategy with high vaccine uptake not only provides direct benefit in the vaccinated cohorts but also extends protection through a herd effect to unvaccinated men.