"It's a little premature to say that even for these three families the process is over," he said.
Powers added that the theory scrutinized in this case was just one of two theories that will be brought before the special court. The other theory maintains that thimerosol alone brought about autism in some children.
"There is no doubt that this is disappointing news," Powers said. "On the other hand, the message to the families is that we will continue to prosecute the cases... follow the science, and see where it leads us."
Still, most in the medical community feel that the preponderance of scientific evidence has already led to the conclusion that vaccines are not responsible for autism.
"It is completely understandable that parents who are desperately looking for a cause of why their child turned out this way will focus on the vaccine," said Dr. Shlomo Shinnar, professor of neurology and pediatrics at Montefiore Medical Center, in Bronx, N.Y. "But there is a large body of scientific data that has refuted this association... It is reassuring that the special masters who are dealing with this were guided by the weight of the available scientific evidence on this important public health issue."
"I am thrilled that this ruling will enable the medical community to speak with conviction about the importance and safety of childhood vaccination," said BethAnn McLaughlin of the Vanderbilt University School of Medicine's department of neurology in Nashville, Tenn. "We recognize that while we are under-funded to study many of the chemicals our families and children come in contact with every day, that the debate about vaccination causing autism should be ended."
Joanna Schaffhausen and Audrey Grayson contributed to this report.