For a new study in the March 2016 Pediatrics, government researchers compared human papillomavirus (HPV) infection rates among U.S. teens and young women before and after vaccination against the cancer-causing virus was introduced in 2006. Using data from the National Health and Nutrition Examination Surveys (NHANES), they found that among females between age 14 and 19 years old, prevalence of the HPV types targeted by the vaccines dropped from 11.5 percent in 2003-2006 to 4.3 percent in 2009-2012.

The study, “Prevalence of HPV after Initiation of the Vaccination Program in the United States” (published online Feb. 22), also showed the HPV prevalence dropped among women age 20 to 24, from 18.5 percent to 12.1 percent. The findings extend earlier studies showing the HPV vaccination program’s impact in the United States. The researchers at the Centers for Disease Control and Prevention (CDC) said this study also provides the first national evidence of an impact on HPV prevalence among females in their 20s. Authors of the study said that while its findings are encouraging, the number of young people receiving the vaccine has increased more slowly than expected. They noted that just 42 percent of girls and 22 percent of boys between the ages of 13 and 17 have received the recommended 3-dose vaccine series. The CDC continues to monitor the NHANES data for further HPV prevalence changes.