Vaccine, preservative do not cause autism

Neither the measles, mumps and rubella vaccine nor a mercury-based preservative used in many childhood shots cause autism, a US health panel said on Tuesday.

Researchers and parents trying to find out what causes autism and its possible recent upsurge should look elsewhere for a culprit, the Institute of Medicine panel said.

"The weight of that evidence is pretty substantial," said Dr Marie McCormick, an expert in child and mother health at the Harvard School of Public Health who chaired the panel.

"The overwhelming evidence from several well-designed studies indicates that childhood vaccines are not associated with autism," she added. The same holds true for a mercury-based preservative called thimerosal which is often used in vaccines, the panel found.

Autism can affect a child's ability to learn, speak and socialise. No one is sure precisely how many children have autism, but some researchers say it could be as common as one in every 1,000 children.

Because autism is usually diagnosed about when children receive many recommended immunisations, some groups believe vaccines are to blame.

A few parents, especially in Britain, have begun to refuse to vaccinate their children and outbreaks of disease have been traced to unvaccinated children.

McCormick said the diseases that are prevented by vaccination were often fatal in the days when they were common childhood occurrences. "These diseases that we are talking about are very, very serious diseases and they are still present in the rest of the world so, they still are a plane ride away," she said.

The Institute's panel, which included experts in pediatrics, family medicine, statistics and epidemiology, had reported in 2001 that there was no proven link between vaccines and autism but said there was not quite enough evidence to be definitive.

Since then, they have reviewed five large epidemiological studies done in the United States, Britain, Denmark, and Sweden that found children who were vaccinated with thimerosal-containing vaccines were no more likely to have autism than children who got thimerosal-free vaccines.

They looked at studies that reported links between vaccines or thimerosal and autism, but found none of them could show a connection.

They searched for evidence of a biological explanation of how immunisations or thimerosal could cause autism, and found none. They listened to advocates and family members who believe vaccines caused autism, as well.

But some groups said the Institute's report was biased. "This report went beyond any other report and this is why I felt it was political," Barbara Loe Fisher, who founded the National Vaccine Information Centre, said in a telephone interview.

She said she would like to see research done by scientists with no connections to the "public health community."

Other groups also promised to continue to battle to prove that vaccines cause autism.

"Another flawed report - government issued or otherwise - will not stop SafeMinds from continuing its mission to foster science and educate the public," said Sallie Barnard, executive director of SafeMinds, one of the groups.

McCormick stressed that the panel was independent of any vaccine maker or of the government and was not paid for its work. She said they considered the possibility that some of the studies were biased.

"We do not feel that the data were manipulated," she said.