Trends in Male and Female Genital Warts Among Adolescents in a Safety-Net Health Care System 2004-2013: Correlation With Introduction of Female and Male Human Papillomavirus Vaccination.

BACKGROUND: Human papillomavirus (HPV) vaccination remains underused in the United States, and few population-level studies on effectiveness exist.
METHODS: We examined trends in rates of genital warts diagnoses and HPV vaccination rates (defined as receipt of 1 or more vaccine doses) among low-income and minority adolescents between 2004 and 2013. Data were obtained from a database containing de-identified medical record information including all outpatient visits to an urban medical center and 6 affiliated community health centers. International Classification of Diseases, Ninth Revision codes were used to determine genital warts diagnoses. We estimated annual rates of genital warts for each period for females and males using an interrupted time-series Poisson regression model.
RESULTS: As HPV vaccination rates in low-income, minority adolescents rose from 0% to 59% (females) and 0 to 41% (males) between 2004 and 2013, genital warts rates decreased from 3.5% (females) and 3.6% (males) to 1.5% (females) and 2.9% (males). Rates of genital warts decreased significantly for both females and males from the prevaccination to the postvaccination periods (P < 0.05 for both comparisons). Genital warts rates for males began to decrease after the introduction of female vaccination and continued to decrease after male vaccination was introduced.
CONCLUSIONS: Introduction of HPV vaccination correlated with lower rates of genital warts among a cohort of low-income and minority adolescents. Rates of genital warts began to decrease in females and males following the introduction of female vaccination and continued to fall after the introduction of male vaccination, indicating that male vaccination may confer additional benefit to both males and females over herd immunity alone, especially when vaccination rates are suboptimal.