The vaccine, Amanda's doctor told them, could prevent potentially deadly cervical cancer. He also explained that the three-dose inoculation would work best if she had it well before becoming sexually active.

This was a doctor that her mom, Linda Zaborowski, had trusted since Amanda was a child. She thought the vaccine sounded like a good idea. But she ultimately wanted her daughter to make the decision.

"If you think this is right for me, you know what's best," the high school freshman told her mom and doctor. "I'll do it."

HPV is a weighty topic that more parents are addressing with their daughters, since the Food and Drug Administration recently approved the vaccine for girls as young as age 9. Some parents, particularly those with preteen girls, are wondering just how much information to share.

Do they simply say it's a vaccine against cancer and leave it at that? Or should they also explain that HPV is a sexually transmitted disease that, among other symptoms, causes genital warts?

Linda Zaborowski says it was clear that she needed to give Amanda, her eldest daughter, more information than less.

"When I was young, my mom said, 'Here's a book.' That's how we learned about sex," says Zaborowski, who is a cafeteria bookkeeper and recess aide at her children's schools in Griffith, Ind., a suburban town near Chicago. "But it's not like that now."

She started to realize that when she sat in on Amanda's fourth-grade lesson on reproductive anatomy a few years ago and discovered that some girls were already menstruating.

Government surveys also have found that about 7 percent of children have had sexual intercourse before age 13, while about a quarter have done so by age 15. And while teen pregnancy rates have steadily dropped since the early 1990s, millions of teens and young adults are contracting sexually transmitted diseases - HPV among the most common.

Researchers at the federal Centers for Disease Control estimate that more than 6 million Americans - many of them teens and young adults get a new infection of HPV each year.

Theresa Rohr-Kirchgraber, an adolescent and internal medicine specialist at the Emory University School of Medicine in Atlanta, says parents need to take those statistics seriously when deciding how to address the HPV vaccine.

"Cervical cancer is real. Sex is real and even though we believe our kid is different and will never have sex until they are married, it is not reality," Rohr-Kirchgraber says.

During medical visits with girls and their parents, she discusses HPV along with routine vaccines for meningitis, as well as the DTaP shot for diphtheria, tetanus and pertussis (also known as whooping cough).

"When you just put it on the list and make it one of the many they need, it becomes less of an obstacle," she says.

Dr. Kenneth Alexander, an associate professor of pediatrics and an infectious diseases expert at the University of Chicago's Comer Children's Hospital, also is a proponent of fully explaining the HPV vaccine to teens.

"Parents only want to talk about cancer prevention. When they talk about STDs, they get pretty uptight," he says. "Teenagers are often more savvy. They're willing to talk about the two issues together."

Alexander has had frank discussions with his own daughters, ages 14 and 17, about the consequences of HPV.

"You can get three doses of the vaccine," he tells them. Or, he says, they might eventually have to deal with a colposcopy - close examination of abnormal cells in the cervix that can be caused by HPV and that often require a biopsy. He also explains various treatments for cervical cancer.

"It's your body," he tells his daughters. "The decision is yours." Alexander and others concede, however, that deciding how much to tell preteens is trickier, even for parents who feel like they have good communication with their children.

Karen Hales, mother of an 11-year-old girl in Slidell, La., is one of those.

"She's a pretty aware child and asks a lot of questions," Hales says of discussions she and her daughter, now a seventh-grader, have had about sex. "It's never been that sit-down talk that you dread. It's kind of been natural."

Even so, while she plans to have her daughter vaccinated for HPV in January when the shots will be available at their clinic, she's still wondering how to broach the subject. Most likely, she says, she'll handle the part about cancer prevention. "And our pediatrician will manage the rest with me in room," she says.

Doctors say parents often think their daughters don't need the vaccine because they're not sexually active. While he wholeheartedly encourages abstinence, Alexander reminds parents that the vaccine is a preventive measure that should be given early ¡ª so even if teens aren't sexually active now, the inoculations guard against future problems.

"It's a little bit like putting money in the college fund. You don't put money in the bank when they're already in college," says Alexander, who also believes the HPV series of shots is "the most important vaccine to come along since the measles vaccine, in terms of the misery it will prevent."

Susan Rosenthal, a pediatric psychologist at the University of Texas Medical Branch at Galveston, says several surveys have found that parents' most frequent concerns are with the seriousness of the illness and whether the vaccine works. "They're much less concerned how the infection is transmitted," she says.

But, Rosenthal believes, parents should still explain how genital HPV is contracted. To that end, she favors the so-called "apprenticeship model," encouraging parents to let teens make increasingly independent decisions about their health as they get older.

"You meet the kid where they are in terms of what information they're ready for," Rosenthal says. Deciding whether to fully explain the HPV vaccine to an 11- or 12-year-old girl, for instance, may depend on whether she is menstruating or showing other signs of puberty.

Rosenthal says a parent might begin by saying, "This is a vaccine for a disease that you can get in your vagina or your cervix. If you get it, it can cause warts and sometimes it can cause cancer."

"If they ask, 'How does it get to your vagina?' then you explain that," Rosenthal adds. "It's a great time to talk about sexuality ¡ª to demystify the pap smear and talk about reproductive health."

Back in Indiana, Amanda Zaborowski is getting set for the second of three shots this fall and has been telling her friends about HPV and the vaccine.

"Most of them have never heard of it," she says.

She and her mom hope parents and teachers will help them learn more.

"If you inform them," her mom says, "they understand the consequences."