U.S. federal regulators have given a preliminary nod to a vaccine that studies show could prevent cervical cancer, which is a leading cause of death among women worldwide. The drug would protect young women and girls against infection with human papilloma virus, a sexually-transmitted disease that infects a majority of women.

The vaccine, called Gardasil, protects women from acquiring human papilloma virus, or HPV, a pervasive, sexually-transmitted disease that studies show is directly responsible for the development of cervical cancer.

Experts say an estimated 80 percent of women are infected with HPV. The disease kills nearly 300,000 women annually.

Merck and Company tested Gardasil on 27,000 people in 33 countries, including young women and girls between the ages of 26 and nine.

Researchers found the drug to be safe and 100 percent effective against two viral strains that are responsible for causing 70 percent of HPV infections.

Based on the data, federal regulators gave the vaccine tentative approval. A final decision is expected in early June.

Richard Haupt, executive director of medical affairs with Merck's Vaccine Division, says studies show the vaccine protects women for at least five years, and it is most effective when given to women years before they become sexually active, such as when they are nine or 11 years old.

"The younger age group is actually very critical to be vaccinated because you're going to get them and you are going to get them before they are exposed to these very important HPV types," he said.

A survey of family doctors by researchers at the University of Cincinnati in Ohio found that 75 percent would recommend the vaccine to the parents of their young patients. At the same time, investigators found some hesitation to offer the vaccine to female patients younger than 17.

Lead investigator Jessica Kahn, a pediatrician at Cincinnati Children's Medical Center, says doctors cited parents' attitudes toward an HPV vaccine.

"So, parental concerns about the safety of the vaccine. Parental concerns about immunizing their child against a sexually-transmitted infection. Parental concern that vaccination would lead to riskier sexual behavior, that kind of thing. The reason that that finding was so interesting to me is that when you look at literature on parental beliefs about HPV vaccines, the great majority of parents are not really worried about those things," she said.

Meanwhile, Merck officials say they are ready to begin marketing Gardasil once the vaccine receives full regulatory approval, which is expected.

In Europe, an experimental vaccine called Ceravix is also proving to be 100 percent effective against two cancer-causing HPV strains. The maker, GlaxoSmithKline, is plans to seek regulatory approval this year.