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PAUL A. OFFIT, MD: There has never been a study that has shown that vaccines cause autism. There was a paper that appeared in The Lancet in the late 1990s that raised the question of whether or not vaccines could cause autism, but that was not a study.

MARK SAWYER, MD: Many studies have been done to look at that question and there's no evidence at all that vaccines are related to autism.

PAUL A. OFFIT, MD: I think, from a parent's standpoint, you know, 'My child is fine, they got a vaccine, then they weren't fine, they developed autism. Could the vaccine have done it?' A perfectly reasonable question. The good news is it's an answerable question.

ALISON SINGER: Because these myths continue to circulate, a lot of families are taking great risks by not vaccinating their children. When you don't vaccinate your child, you're doing absolutely nothing to reduce the risk that they'll be diagnosed with autism, but you're absolutely increasing the risk that they'll contract a vaccine-preventable disease.

MARY BETH KOSLAP-PETRACO, DNP(c), CPNP: It is clearly not the vaccines. We've proven it's not the vaccines. It's really time to look elsewhere for the causes of autism.

ALISON SINGER: We know that autism is highly genetic. It's probably the most genetically linked of the developmental disabilities. We know this from twin studies.

We know that in identical twins, if one is diagnosed with autism, the likelihood that the other twin will also be diagnosed with autism is around 90%: whereas with fraternal twins, who don't share all of their DNA, the likelihood if one is diagnosed with autism that the other will also be diagnosed with autism is one in 15, which is the same for all siblings. So we know that there's a highly, a strong genetic component to autism.