HPV Vaccine Seems To Be Working, Abnormal Pap Test Results Lower, Study Shows

The findings show the vaccine, named GARDASIL, appears to prevent the development of cell changes that lead to cervical disease, the researcher said.

In testing GARDASIL reduced abnormal Pap test results by 43 percent compared to women not given the vaccine. The 43 percent reduction was for tests that found pre-cancerous changes called high-grade squamous intraepithelial lesions (HSIL) more than three years after women were given the vaccine.

GARDASIL reduced other abnormal Pap results, including milder pre-malignant cell changes, by 16 to 35 percent compared to women not given the vaccine.

While the findings are not definitive that GARDASIL prevents cancer, they do signal 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, M.D., associate professor in the UAB Division of Gynecologic Oncology and the doctor chosen to present the data.

"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."

The results are a compilation of three separate trials involving more than 18,000 women, ages 16 to 26, in the United States, Europe and Asia. All test subjects had normal Pap smear readings at the start of the trial.

In addition to the drop in unwanted Pap results, the study found invasive procedures like cervical biopsies were performed up to 42 percent less in GARDASIL recipients compared to women not given the vaccine, Huh said.

GARDASIL is approved to fight the human papilloma virus (HPV) strains believed to cause 70 percent of cervical cancers and more than 90 percent of genital warts.

For many unvaccinated women HPV infections clear up naturally without causing any cervical problems, as do many pre-malignant lesions. In other cases, HPV prompts cell changes that can gradually put women at greater risk of cervical cancer.

Nearly 25 million U.S. women between the ages of 14 and 59 are infected with HPV, and the annual cost of screening and treating cervical abnormalities is about $4 billion, according to a statement from the Society of Gynecologic Oncologists. "Dr. Huh's study concludes that the trials covered in this paper indicate an overall benefit of vaccination," the society's statement said.

The findings were presented March 10 at the annual meeting of the Society of Gynecological Oncologists held in Tampa.