"The vaccine has been pretty well-received so far," says Neal Hoffman, an attending physician at Montefiore School's health center in the Bronx. "But some parents—especially those with younger children—think it's premature to talk to their daughters about sexually transmitted diseases."

While some parents worry about introducing the topic of sex to their preadolescent daughters, a growing number of doctors and scientists have voiced concerns regarding the vaccine—concerns they say are much more pressing.

Every year, 9,700 new cases of cervical cancer are diagnosed in the U.S., and 3,700 women die of the disease. Gardasil's makers claim that 70 percent of those cases could be prevented by the vaccine, but a May issue of the New England Journal of Medicine raised several questions about Gardasil's effectiveness. Among other things, the vaccine may be unsafe to give with other childhood vaccines, and it may be 10 to 15 years before scientists know whether booster shots are needed. Later that month, a watchdog group released FDA documents detailing 1,637 adverse reactions to the vaccine in the year since it was approved. While most of the reported reactions were not serious, they did include three deaths, 16 miscarriages, and numerous cases of Guillain-Barre syndrome (GBS), an immune disorder that can result in paralysis.

Meanwhile, 75,000 doses have been distributed to New York City's school-based health clinics, and while the vaccine is not mandatory in New York, it has been added to the list of shots that parents are routinely encouraged to have their children get.

Dartmouth doctor Diane Harper, who received funding from Merck and was a lead researcher in the development of Gardasil, acknowledges that "there are still many unknowns" about the vaccine. But she says the real issues surrounding it have nothing to do with fears of a promiscuity outbreak.

"We have no evidence that HPV is sexually transmitted," says Harper, who directs Dartmouth's Gynecological Cancer Prevention Research Group. "All we know is that it's a skin-to-skin transmission." While she acknowledges that people who have sex are more likely to have HPV, Harper points to cases of 3-year-olds contracting the virus, adding, "Can you transmit it by your finger, for example? We have no idea."

The vaccine is currently recommended for girls age 9 to 26, with the vaccine's proponents arguing that the earlier a girl is vaccinated, the better. As the number of sexual encounters increases, so does the likelihood of a person's having already been infected with one or more of the virus's strains. Once you've been infected by a strain, the vaccine cannot protect you from it. But while there's a test that can tell whether you've had HPV, there is no way of knowing which strains your immune system has battled—hence the race by Gardasil's proponents to vaccinate before any sexual activity.

However, some doctors—including Harper—are asking their colleagues to curb that enthusiasm.

"This vaccine will reduce the incidence of cervical cancer in the U.S.," she says. "But it does not have the potential to eradicate the disease."