MMR not linked to autism say scientists

Thursday, 3 March 2005 12:00 AM

A new study has added more weight to scientific evidence that the triple measles, mumps and rubella (MMR) vaccine is not linked to the increasing incidences of autism.

Researchers analysing autism rates in more than 30,000 children in the Japanese city of Yokohama found the incidence of autism spectrum disorders was unaffected when the jab was withdrawn in 1993.

Controversy has dogged the MMR vaccine in the UK since 1998, when Dr Andrew Wakefield and colleagues wrote in The Lancet medical journal that the immunisation might trigger autism.

The vast majority of the scientific community roundly rejected the work as it was based on only 12 children and contained serious flaws. The Lancet later said it should never have published the paper because Dr Wakefield was subject to a conflict of interest, and the findings were eventually retracted by many of the co-authors.

However, many concerned parents opted for single vaccines or avoided the immunisation programme altogether. Vaccine coverage dropped, prompting outbreaks of measles and fears of an epidemic.

There has never been any epidemiological evidence to link MMR to autism, but the Japanese study is the first to examine what happens when the vaccine is withdrawn, New Scientist reports.

Hideo Honda of Yokohama Rehabilitation Centre and colleagues analysed the records of 31,426 children born in the city between 1988 and 1996. They found the rate of autism, diagnosed by the age of seven, continue to rise despite the withdrawal of MMR in 1993 because of fears the anti-mumps component was causing meningitis.

Co-author Professor Michael Rutter, of the Institute of Psychiatry, told BBC News that the findings "rubbish" the claim that MMR is having a general effect to the rates of autism.

"If there was a true causal relationship between MMR and autism, one would have expected rates to fall after the vaccine was withdrawn," he said.

Many scientists believe that environmental factors or changes in diagnostic criteria have caused the increased incidence in autism spectrum disorders.

But those who blame MMR for their children's autism are adamant more research is needed.

The study appears in the Journal of Child Psychology and Psychiatry.

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