Parents asked a doctor who specializes in vaccines to answer some of their questions as part of a package of stories about parents' fears surrounding vaccines and autism. Dr. Gregory Poland, director of the Mayo Clinic Vaccine Research Group, answered.

Second of two parts: The Rotashield story has become well-known in the controversy about childhood vaccines. For advocates of vaccination, it shows that the system catches even rare problems and corrects them. But for those who suspect that vaccines cause autism, Rotashield proves that unsafe compounds sometimes make it to market.
First of two parts: Debate rages over need for vaccines
Interactive: Compare the data