ATLANTA (AP) -- Federal health officials say about one in four teenage girls have gotten the vaccine that prevents cervical cancer.

Gardasil is a three-shot series that targets the strain of a virus that causes 70 percent of cervical cancers. Health officials recommend that girls get the shots when they are 11 or 12, before they become sexually active.

Proponents of the vaccine had been hoping for much higher vaccination rates. They say the shots could dramatically reduce the nearly 4,000 cervical cancer deaths in the country each year.

But experts say many families are cautious about the safety of new vaccines. It's also expensive, and questions remain about whether it confers lifetime immunity or if a booster shot will be needed.

Merck, the company that makes Gardasil, says it's pleased with the vaccination rate.

(Copyright 2008 by The Associated Press. All Rights Reserved.)