Vaccines do not cause autism, a special court ruled Thursday in three cases regarding a long-term medical controversy.

The evidence to support claims of a vaccine-autism link “is weak, contradictory and unpersuasive,” said Special Master Denise Vowell. It appears that the petitioners in these three cases were the victims of “bad science” and of a scientifically not-sustained fear that vaccines may be responsible for autism and other health problems.

Federal health agencies and scientific groups have strongly argued that there is no link between vaccines and autism and warned that unvaccinated persons may be at risk of acquiring measles or other contagious diseases themselves and also transmitting the diseases to others, including children who are too young to be vaccinated. The U.S. Department of Health and Human Services said it continues to support research “to better understand the cause of autistic disorders and develop more effective methods of treatment.”

Doctors hope that the decision will put an end to parents’ fear and will finally settle the issue of MMR vaccine as an alleged cause of autism.

The connection between thimesoral, a mercury-based preservative found in many childhood vaccines, and autism was first suggested by study published in the British journal the Lancet. Scientists became more interested on this possible connection after an increase in the incidence of autism, which was registered around the same time.

Autism is a brain development disorder that appears before a child turns three years old; it has a serious impact on social interaction and communication. The disease, characterized by poor social interactions, impaired communication and repetitive behavior, affects as many as 1 in every 150 kids in the U.S., according the Centers for Disease Control and Prevention. In the past few years, more researchers have been exploring the possibility that the disorder involves an interaction of genetics and environmental factors.