"The theory, that there may be underlying genetic defect that results in or can be somehow activated by some environmental process or insult, and that this in turn leads by some biological mechanism to autism is a valid theory, and it is a theory being pursued by the autism research community," Schaffner said.
"But any subset of this theory is a hypothesis, and you don't draw conclusions from a hypothesis."
Dr. Gary Mirkin, CEO of Allied Pediatrics of New York in Great Neck, agreed.
"This case … looks like a child who had a very rare pre-existing, underlying condition that may or may not have been aggravated by the administration of multiple vaccines to result in a regressive form of autism or something that appeared to be autism," Mirkin said. "If this child had never had a vaccine, it is not inconceivable that the same scenario may have developed if the child was confronted with a serious infection or even a series of multiple infections."
Schaffner said holding back on kids' vaccinations could expose them to risk of sickness or death from other conditions, including measles and polio.
"These diseases that affected childhood are now not known by this generation of parents, so there's no balancing of concern," he said.
"Without vaccination, these disease will return, and they will spread."
Ren Holding of the ABC News Law & Justice Unit contributed to this report.