One day Hannah Poling was a happy, babbling toddler who would wave to her father as he headed to work and say, "Bye-bye, Daddy." The next she was a screaming, wailing 18-month-old who would sit for hours, staring into space and refusing to be touched or fed. Within days of receiving nine vaccines during a visit to her doctor, including ones missed from previous appointments, her mother, Terry, says, "It was like Hannah became another person." Months later she was diagnosed with autism. "The Hannah we knew was gone."

Today, as the 9-year-old redhead walks in circles and talks to herself at the family's toy-filled home in Athens, Ga., she is unaware of her controversial role at the center of a national debate. On the one side are the parents of autistic children (among them Hollywood stars like Jenny McCarthy) who believe that vaccines—specifically those containing the mercury-based preservative thimerosal—triggered or caused their kids' neurological disorders. Pitted against them are academic and government scientists whose studies show no link between childhood shots and autism. While 4,800 claims are backed up in a federal vaccine court, the Polings recently became the first family of the group to receive the promise of a financial settlement and an acknowledgment—albeit of limited scope—that vaccines contributed to Hannah's symptoms. "This concession represents an important victory," says attorney Cliff Shoemaker, who represents the Polings. "For the first time that I am aware of, the government has conceded that there is a way that vaccines can result in autism."

Scientists and physicians strongly disagree that the case suggests any such thing. According to a court document leaked on the Internet, it was concluded in the so-called vaccine court (where the case of Michelle Cedillo, reported in PEOPLE July 2, 2007, is still pending) that the shots given to Hannah in July 2000 "significantly aggravated an underlying mitochondrial disorder," a disease that impedes a cell's ability to generate energy. That, in turn, produced a brain injury that resulted in autistic behavior.

While the Polings will now be compensated for Hannah's care (the amount has not yet been determined), the court stopped short of drawing a link between vaccines and autism. "Let me be very clear that the government has made absolutely no statement indicating that vaccines are a cause of autism," says Dr. Julie Gerberding, director of the Centers for Disease Control and Prevention. As a precautionary measure, thimerosal has been removed from all childhood vaccines, save for some flu inoculations, since 2001. Even so the autism rate continues to rise, according to a recent study by the California Department of Public Health. That increase, says Eric Fombonne, a professor of epidemiology at Montreal's McGill University, "is certainly not due to vaccines."

Some supporters of the autism-vaccine theory have stopped inoculating their children. But that's hardly the Polings' position. "We're not trying to say vaccines are bad," says Terry, 47, who is both a nurse and a lawyer. "We don't want a measles or diphtheria outbreak." Rather, she says, she and her husband, Jon, 37, a neurologist, "just want the government and scientists to look more closely at what vaccines we're giving children and how we're giving them."

After Hannah was diagnosed, the Polings, who have a healthy 10-year-old son, focused on assorted therapies (behavioral, occupational, speech). "I was really hoping she'd recover," Terry says. But problems continue to accrue. At 7, Hannah developed a seizure disorder. More recently she's been hitting and biting herself, and leaving the house without warning. "The safety issue is one of the hardest," says Jon. "We've put locks on the windows, bolts out of her reach and a voice-activated alarm system on the windows and doors."

In her special-needs class at school, Hannah gets along with other students—but nobody invites her home to play. "She doesn't have friends, but she has her brother Nikolaus, and he is the most incredible therapist," says Terry. Like so many parents of autistic kids, the Polings worry what will happen after they're gone. "Hopefully with this settlement," says Jon, "Hannah will be taken care of, and that is very reassuring."

  • Contributors:
  • With Daniel S. Levy.