What happened to little, red-haired Hannah Poling is hardly unique in the world of autism. She had an uneventful birth. And then, right after receiving a bunch of vaccines, she fell ill. Hannah, now 9, recovered from her acute illness but she lost her words, her eye contact and, in a matter of months, began exhibiting the repetitive behaviors and social withdrawal that typify autism. Parents of kids like Hannah have been fingering vaccines - and, in particular, the mercury-based vaccine preservative thimerosal - as a cause of autism for over a decade, but researchers have repeatedly failed to find a link. What's unique about Hannah's case is that for the first time federal authorities have conceded a connection between her autistic symptoms and the vaccines she received, though the connection is by no means simple. A panel of medical evaluators at the Department of Health and Human Services concluded that Hannah had been injured by vaccines - and recommended that her family be compensated for the injuries. The panel said that Hannah had an underlying cellular disorder that was aggravated by the vaccines, causing brain damage with features of autism spectrum disorder (ASD).