The proportion of abnormal results of Pap cytology testing decreases significantly after girls and women are given vaccine against human papillomavirus, according to a presentation at the annual meeting of the Society of Gynecological Oncologists. Researcher at the University of Alabama at Birmingham concluded that the vaccine, GARDASIL, appears to prevent development of cellular changes that lead to cervical disease.

In the current study, researchers analyzed data for three separate trials involving more than 18,000 women, ages 16 to 26 years, in the United States, Europe and Asia. All test subjects had normal cytology results at the start of the trial.

During more than three years of follow-up, the vaccinated group had a decrease of 43 percent in high-grade squamous intraepithelial lesions compared with the unvaccinated group. In addition, invasive procedures including cervical biopsies were performed up to 42 percent less in vaccine recipients compared with unvaccinated women.

Vaccination reduced other abnormal results, including milder premalignant cell changes, by 16 to 35 percent compared with women who were not given the vaccine.

While the findings are insufficient to prove that the vaccine prevents cancer, they do signal that the vaccine will spare thousands of women a diagnosis of cell abnormality or malignant changes that may lead to more tests and possibly surgery, said Warner Huh, MD, associate professor in the Division of Gynecologic Oncology and study presenter.

"Clearly the vaccine's benefits include something that can be appreciated by women and daughters fairly quickly," Huh said. "This is a positive first sign, and it will take many more years to know definitively if the vaccine prevents cancer."