A study involving nearly 1,400 girls enrolled in a Kaiser Permanente health plan in Atlanta is the first to compare medical records for vaccinated and unvaccinated girls.
The researchers didn't ask girls about having sex, but instead looked at "markers" of sexual activity after vaccination against the sexually transmitted human papillomavirus, or HPV. Researchers examined records on whether girls had sought birth control advice; tests for sexually transmitted diseases or pregnancy; or had become pregnant.
Very few of the girls who got the shots at age 11 or 12 had done any of those over the next three years, or by the time they were 14 or 15.
The study was published online in Pediatrics. Three of the study's four co-authors reported having done previous research funded by Merck, the vaccine's maker