According to a study in the Journal of Infectious Diseases, the prevalence of human papillomavirus (HPV) types included in the vaccine fell by more than half among adolescent girls in the years soon after the vaccine's introduction. The lead author works for the CDC.
Researchers compared the prevalence of HPV between the pre- and post-vaccine eras (2003–2006 vs. 2007–2010) using National Health and Nutrition Examination Survey data. Data was collected from cervicovaginal swab specimens from roughly 4200 females (aged 14 to 59) in each time period examined.
The prevalence of HPV vaccine types (6, 11, 16, or 18) among females aged 14 to 19 decreased from 11.5% in the prevaccine period to 5.1% in the latter period. One third had received at least one dose of vaccine. No declines were observed in other age groups. Sexual behaviors did not appear to differ between the two periods.
Markowitz, Laura E., M.D. et al. "Reduction in Human Papillomavirus (HPV) Prevalence Among Young Women Following HPV Vaccine Introduction in the United States, National Health and Nutrition Examination Surveys, 2003–2010." J Infect Dis. (2013) doi: 10.1093/infdis/jit192 First published online: June 19, 2013. http://tinyurl.com/l9xyhoo (accessed June 20, 2013). [Abstract free]