The vaccine protects against strains of the virus that cause about 70 percent of cervical cancers.
Health officials recommend that girls get the shots when they are 11 or 12, if possible, before they become sexually active.
Also, age 11 is when kids are generally due for another round of vaccinations.
The survey only covered children in the 13-17 age range.
Vaccine proponents had been hoping for much higher vaccination rates, saying the shots could dramatically reduce the nearly 4,000 cervical cancer deaths that occur each year in the United States.
But many families are cautious about the safety of new vaccines, said Patti Gravitt, a Johns Hopkins University associate professor of epidemiology.
Other things about the vaccine may give some families pause. It is expensive, retailing for about $375, although many health insurers now cover it. And there are questions about whether it confers lifetime immunity or if a booster shot will be needed.
"Some parents may be adopting the attitude with their daughters that, 'Well, you're still young. I can wait a couple more years before you're sexually active,"' said Gravitt, who was not involved in the research.
"My personal opinion is that this seems quite reasonable after the first year," Gravitt said, of the 25 percent vaccination rate.
Merck officials said they were pleased with the vaccination rate.
The Centers for Disease Control and Prevention based the study on household telephone surveys done in late 2007. The survey results cover the time frame from when the vaccine came on the market in mid-2006 to when the survey questions were answered.
The results are based on nearly 3,000 teens ages 13 to 17 for whom the researchers could verify vaccination information through medical records.
Of the girls in the survey, 25 percent had received at least one Gardasil shot. That's about 2.5 million of the 10 million girls in that age group.
The CDC, which has been promoting other shots for adolescents, also studied other teen vaccination rates.
About 32 percent of teenagers got a recommended meningitis shot, up from 12 percent in a 2006 survey. Also, 30 percent got another relatively new shot, one that guards against tetanus, diphtheria and whooping cough. That's up from 11 percent in the survey the year before.
About 75 to 90 percent of children have had the better-known vaccinations that have long been required by schools, such as chickenpox, hepatitis B and measles, mumps and rubella, the study found.
"There's a lot of good news in the survey results," said Dr. Lance Rodewald, director of the CDC's Division of Immunization Services.
But while the study showed improvements in the number of preteens and teenagers being protected against serious diseases, health officials are pushing for 90 percent immunization rates for all recommended shots, he said.
