The morning after Emily Cunningham got a shot of Gardasil, the new vaccine that protects against four strains of the human papilloma virus(HPV)that can cause cervical cancer and genital warts, she woke up with a headache, and neck and back pain. By 9 p.m. that evening in April, she had a fever so high "you could feel the heat rising from her a foot away," according to her mother, Laurie. She was delirious during the night, and the following day couldn't walk without assistance. Bedridden for nearly a week, the 18-year-old from Wyoming missed school, and took Tylenol every four hours. "If Emily had been the only one to get sick we would have said she must have had something else [like the flu]," explained Laurie, "but we know of three other students to have reactions, that is why we are concerned."

Emily's story is only one of 1,637 complaints involving Gardasil, filed as of May to the Vaccine Adverse Event Reporting System(VAERS), a national surveillance database sponsored by the Food and Drug Administration(FDA)and the Centers for Disease Control and Prevention(CDC)in the United States. One could discount what happened to Emily because she had a flu shot that same day, but other really bad reactions have been reported, including seizures, paralysis -- and worst of all, three deaths, including one girl who "died of a blood clot three hours after getting the Gardasil vaccine," reads one complaint. Elsewhere in the world there have been reports of similar reactions. In Melbourne, Australia, where a national HPV vaccination program started in April, 26 girls reportedly fainted and were mildly paralyzed after getting one shot each.

In almost every instance, the response of medical authorities and government officials is the same: bad reactions are rare. When they do occur, there's no evidence that Gardasil was the cause. Arguably, both points could be true. Some say the problem, however, is that no one really knows, medically speaking, just how dangerous this vaccine could be. "Usually at this stage in the life span of a vaccine we would not have this kind of action," Maclean's has heard from Abby Lippman, an epidemiologist at McGill University who recently aired her concerns about the speed with which Gardasil has been adopted in the Canadian Medical Association Journal. "We're making guesses that it's going to last long, that [we're immunizing] the right age [of girls], and that it's effective. We don't have a solid basis for this thought."

And yet, nearly every province in Canada has, in recent weeks, put forth some plan to implement an HPV vaccination program that will see the mass inoculation of an entire generation of girls -- some as soon as this September -- with no serious acknowledgement of the potential health risks they might face. While everyone debates the moral and political consequences of endorsing Gardasil, the fundamental, essential medical and scientific debate remains untouched. So, in a few weeks, when thousands of girls concerned about Facebook and who will be in their class this year -- not HPV -- go back to school, many will become part of the biggest Canadian science experiment in decades. They will be the guinea pigs.

To find out the worst case scenario when it comes to Gardasil, one need only hear the stories of parents whose children have become ill or died after receiving the vaccine. Recently, one angry father from Chicago phoned up John Driscoll, an attorney at the law firm Brown & Crouppen in St. Louis, Mo. Shortly after receiving Gardasil, his daughter was diagnosed with Guillain-Barré syndrome, an autoimmune disease. It starts with tingling sensations in the legs, which then travel to the upper body, and finally become so intense in the muscles they paralyze, though often they diminish over time. "He believes it was linked," says Driscoll, and wants to sue Merck & Co., Inc., the U.S. pharmaceutical company that manufactures Gardasil. This will be the first such lawsuit, but Driscoll, who believes the vaccine was rushed to market, predicts that, "unfortunately, we'll get more and more calls about this in the future."

In fact, Guillain-Barré syndrome is one of the more serious adverse reactions noted in the hundreds of complaints filed to VAERS. "When you go to your doctor's office, the list of symptoms is very short: dizziness, fainting. But there's a whole laundry list of potentially serious side effects," says Dee Grothe, an investigator at the Washington-based watchdog organization Judicial Watch, which filed freedom of information requests to access details about negative reactions relating to Gardasil. "This is information that everybody receiving the shot should know," she says.