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PAUL A. OFFIT, MD: When the question was raised in the late 1990s that the MMR vaccine might cause autism, very quickly the academic and public health community responded by doing studies—frankly 12 studies—in hundreds of thousands of children that did or didn't receive vaccines to see whether vaccines were a risk—because they took those parents' concerns seriously—and found that vaccines really didn't increase the risk, which is consistent with everything we know about autism, which is that it's something probably that occurs when the child is still in the mother's womb.

MARK SAWYER, MD: Thimerosal, which was a product in vaccines which was implicated as a cause of autism, has been taken out of all the vaccines that we give in pediatrics now. And despite that, the rates of autism have continued to go up. So, we've taken away the purported agent in vaccines and autism continues.

ALISON SINGER: Vaccines are probably the best studied environmental trigger with regard to autism. We really need to move on and start to fund other types of studies looking at other potential environmental triggers for autism.

If we keep asking the same questions, we're not going to find new answers. We need to ask new questions so that we can finally understand what does cause autism and develop new treatments that will actually help our family members.