NEW YORK (Reuters Health) - A nationwide study following all children born in Denmark since 1991 found no evidence that the measles, mumps and rubella (MMR) vaccine causes autism in children.

The investigators followed 537,303 children from birth, noting who received the MMR vaccine and when, and who developed autism. Dr. Kreesten Meldgaard Madsen of the Danish Epidemiology Science Centre and his colleagues found that unvaccinated children were just as likely as those given the MMR vaccine to develop autism, and autistic children who had been vaccinated were just as likely to develop the condition before the vaccine as after.

"These children were (developing autism) no matter whether or not they were vaccinated," Madsen told Reuters Health.

Whether vaccines trigger autism has been the subject of much debate recently, and Madsen said he hopes these findings help settle things once and for all.

"I don't think this study leaves room for any doubt as to whether MMR vaccine causes autism," Madsen said. "I don't think we can get much closer to the answer of this question."

Autism is a condition marked by behaviors that first appear during childhood, often during the years when children receive vaccines. Children with autism have trouble playing and interacting with others and difficulty communicating, and may perform certain behaviors or routines repetitively.

During the study, published in the November 7th issue of The New England Journal of Medicine, Madsen's team reviewed the medical records of every child born in Denmark between January 1991 and December 1998. The researchers determined whether or not each child had been vaccinated or developed autism, and when, through national registries that track the health of Danish citizens.

The authors note that 82% of the children received the MMR vaccine. A total of 738 children were eventually diagnosed with a form of autism, a similar rate to that reported by previous investigators.

Madsen and his team discovered that children who had received the MMR vaccine were just as likely as those who were not vaccinated to develop autism, and vaccinated children had an equal chance of developing the condition before and after receiving the vaccine.

In an interview with Reuters Health, Madsen said that he could understand why parents are concerned that a vaccine might be the cause of autism. "Once you get sick, you start looking for a cause," he explained.

And although the rate of autism appears to have risen as more children have received the MMR vaccine, Madsen said that that does not mean the two factors are linked. Rather, he suspects that the rate has not changed, and professionals have simply gotten better at diagnosing the condition, perhaps due to growing awareness on the part of parents and professionals.

He added that he hopes these findings also help parents remember why they need to vaccinate their children, and that fears of autism should no longer deter them from doing so. The MMR vaccine offers protection against diseases that can cause severe illness and even death in children, he said. "This is a very serious disease we're trying to prevent," he said.

SOURCE: The New England Journal of Medicine 2002;347:1477-1482.

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