In spite of recent courtroom losses, parents who blame their children’s autism at least in part on childhood vaccines say their legal battle is far from over.

“We’ve always been in it to the very end,” said Theresa Cedillo of Yuma, Ariz., whose autistic daughter Michelle became the focus of a key test case at the U.S. Court of Federal Claims in 2007. Even though the special master in the case ruled against her, Cedillo said, “I am optimistic. We have met our burden.”