By DONALD G. McNEIL Jr.

In a further blow to the antivaccine movement, three judges ruled Friday in three separate cases that thimerosal, a preservative containing mercury, does not cause autism.

The three rulings are the second step in the Omnibus Autism Proceeding begun in 2002 in the United States Court of Federal Claims. The proceeding combines the cases of 5,000 families with autistic children seeking compensation from the federal vaccine injury fund, which comes from a 75-cent tax on every dose of vaccine.

Families of children hurt by Vaccines — for example, who suffer fatal allergic reactions — are paid from it but are unable to sue the vaccine manufacturer. The fund has never accepted that Vaccines cause autism; the omnibus proceeding, with nine test cases based on three different theories, was begun in 2002.

The antivaccine groups also lost the first three cases, which were decided in February 2009 by the same three judges, known as special masters. All three rulings were upheld on their first appeals.

Defenders of Vaccines said they were pleased by Friday’s decision, while opponents were dismissive, saying they would never get a fair ruling from the omnibus arrangement.

In the three cases brought against the government, by the parents of Jordan King, Colin R. Dwyer and William Mead, all three special masters used strong language in dismissing the expert evidence from the families’ lawyers.

The master in the King ruling emphasized that it was “not a close case” and “extremely unlikely” that Jordan’s autism was connected to his Vaccines. The master in the Dwyer case wrote that many parents “relied upon practitioners and researchers who peddled hope, not opinions grounded in science and medicine.”

Patricia Campbell-Smith, the master in the Mead case, also dismissed two subarguments made by a few opponents of Vaccines, saying they “have not shown either that certain children are genetically hypersusceptible to mercury or that certain children are predisposed to have difficulty excreting mercury.”

She also echoed a contention by vaccine defenders that a shot is safer than a tuna sandwich. “A normal fish-eating diet by pregnant mothers” is more likely to deposit mercury in the brain than Vaccines are, she wrote.

In a telephone press conference after the rulings, Dr. Paul Offit, director of the Vaccine Education Center at Children’s Hospital of Philadelphia and the inventor of a rotavirus vaccine from which he receives royalties, praised the decisions, saying: “This hypothesis has already had its day in scientific court, but in America we like to have our day in literal court. Fortunately, we now have these rulings.”

Fears of thimerosal emerged more than a decade ago and have cast a pall over Vaccines ever since, even though it has been removed from most of them. The fear has caused some parents to avoid them and made outbreaks of diseases like measles and whooping cough more likely.

Even with this decision, Dr. Offit said, “it’s very hard to unscare people after you’ve scared them.”

The Coalition for Vaccine Safety, a group of organizations that believe Vaccines cause autism, dismissed the rulings.

“The deck is stacked against families in vaccine court,” said Rebecca Estepp, of the coalition’s steering committee. “Government attorneys defend a government program using government-funded science before government judges. Where’s the justice in that?” The coalition claims to represent 75,000 families.

Amy Carson, founder of Moms Against Mercury, who has a son with brain damage, called the vaccine court arrangement “like the mice overseeing the cheese.”

The vaccine injury fund and the court overseeing it were created in 1988 after judgments in state court lawsuits over Vaccines became so inconsistent and so expensive that vaccine companies started quitting the American market.

The third theory, that measles vaccine causes autism, is still to be ruled on by the special masters. But Lisa Randall, a lawyer with the Immunization Action Coalition, which defends Vaccines, said she believed some of the test cases had been “abandoned” by the families that brought them after the 2009 decisions dismissed a variant of the same theory.

3 Rulings Find No Link to Vaccines and Autism