CINCINNATI, July 9 (UPI) -- The human papillomavirus vaccine has reduced the infection in immunized U.S. teens, but also in teens not immunized, U.S. researchers found.
Lead author Dr. Jessica Kahn of Cincinnati Children's Hospital Medical Center said the study is believed to be the first to show a substantial decrease in HPV infection in a community setting as well as herd protection.
Herd protection is a decrease in infection rates among unimmunized individuals that occurs when a critical mass of people in a community is immunized against a contagious disease.
The first HPV vaccine, licensed in June 2006, is recommended for girls and women ages 11-26 to reduce rates of HPV infection, which can lead to cervical cancer.
In 2006 and 2007, Kahn and colleagues at Cincinnati Children's recruited 368 young women ages 13-16. The young women had sexual contact but none had been vaccinated.
In 2009 and 2010, they recruited a different group of 409 young women in the same age range, more than half of whom had received at least one dose of the vaccine. The researchers compared pre- and post-vaccination HPV prevalence rates.
The study, published online in the journal Pediatrics, found the prevalence of vaccine-type HPV decreased 58 percent overall, from 31.7 percent to 13.4 percent. The decrease was high among vaccinated participants -- 69 percent -- but also was substantial for those who were unvaccinated at 49 percent.