Temporal Trends in the Incidence of Anogenital Warts: Impact of Human Papillomavirus Vaccination.

BACKGROUND: Studies in countries with high human papillomavirus (HPV) vaccination coverage have demonstrated marked reductions in anogenital wart (AGW) incidence. Our goal was to assess the impact of HPV vaccination in a population with suboptimal coverage by comparing AGW incidence trends in the years before and after vaccine introduction. METHODS: We conducted a retrospective analysis of AGW incidence trends using an ecologic study design among 11- through 39-year-olds enrolled at Kaiser Permanente Northwest. We defined incidence as the proportion of persons who had a new AGW diagnosis for each calendar year in the prevaccine periods (2000 through 2006 for female individuals, 2000 through 2010 for male individuals) and the postvaccine periods (2007 through 2016 for female individuals, 2011 through 2016 for male individuals). We also described cumulative HPV vaccination coverage. RESULTS: The average annual AGW incidence rates in the prevaccine periods were 27.8 per 10,000 in female individuals and 26.9 per 10,000 in male individuals. In the postvaccine periods, AGW incidence rates decreased by 31% (P < 0.001) in female individuals and 10% (P = 0.006) in male individuals; the largest reductions were observed in 15- to 19-year-old female individuals (67%, P < 0.001) and male individuals (45%, P < 0.001). Three dose HPV coverage rates were less than 50% in all age groups and both sexes. CONCLUSIONS: In a population of young adults with moderate HPV vaccination coverage, we observed declines in AGW incidence among both female and male year after the introduction of HPV vaccination. The largest incidence reductions were observed in 15- to 19-year-olds who were most likely to have been vaccinated.