Thousands of American parents who say their children developed autism from vaccines against certain diseases have suffered a legal setback. A special court in Washington D.C. rejected claims by three of the families that vaccines were to blame for their children's autism.

It said the families were victims of bad science. But some consumer advocates say more research is needed before the link can be ruled out.

Angela and Rolf Hazlehurst have a nine-year-old son with autism. The couple says William developed autism from vaccines including one against measles, mumps and rubella.

Another couple - Theresa and Michael Cedillo - made a similar claim.

But recently, a special court in Washington ruled that the evidence did not prove the alleged link between vaccines and autism.

"This is a setback," Angela Hazlehurst said. "But it does not mean we are going to stop fighting for that little boy."

Autism is a complex brain disorder that impedes a person's ability to communicate or interact with others. About one of every 150 children in the U.S. have been diagnosed with the condition. 

About 5,000 families say their children developed autism from vaccinations. They are seeking compensation through a government program.

Dr. Bill Shaffner of Vanderbilt University says the court's decision should reassure parents about the vaccine against measles, mumps and rubella. 

"The families will have to digest this ruling, of course, and some will be persuaded by the logic of the judges, others perhaps not," he said.

Some of the plaintiffs have filed claims about other vaccines and ingredients in them.

Barbara Loe Fisher heads a consumer group that says more research is needed. She says each claim should be considered on its own merits.  

"You will find some people will get a vaccination and have no problem," she explained. "Others will die or have severe health problems that will lead to chronic disability and illness."

Fear of a link between vaccines and autism has  led many American parents not to vaccinate their children against diseases like measles.

More than 100 cases of measles were reported in the U.S. in the first half of 2008. In almost all the cases, the victims had not been  vaccinated.

Dr. Peter Hotez  of George Washington University says vaccines save lives.

"Let us remember what we are using these vaccines for. We are using them to prevent measles, we are using them to prevent polio, we are using them to prevent pertussis otherwise known as whooping cough, we are using them to prevent tetanus. These are the leading childhood killers in the world," he said.

U.S. government scientists hope studies that show vaccines do not lead to autism will persuade more parents to vaccinate their children.