11/07/2002

By SHERRY JACOBSON / The Dallas Morning News

A major new study of half a million children in Denmark offers further evidence that there is no connection between a common childhood vaccination and the subsequent development of autism.

Researchers looked at the incidence of autistic disorders among 440,655 Danish children who had received the standard vaccine to prevent measles, mumps and rubella. Then they compared how often the same disorders appeared in a group of 96,648 children who were not vaccinated.

The eight-year study, published Thursday in The New England Journal of Medicine, found the same risk of autism in both groups, providing what the authors called "strong evidence" against the hypothesis that the vaccine could be causing autism.

A number of smaller studies in recent years have likewise established no connection.

"Few studies can be said to be conclusive, but I think this is as close as we can get," said Dr. Kreesten Meldgaard Madsen, an epidemiologist at the Danish Epidemiology Science Center in Arhus, Denmark, and the study's lead investigator.

Eight years of records

The study was drawn from the meticulous health records kept of every child born in Denmark from 1991 through 1998.

Each childhood vaccination was recorded, as well as subsequent diagnosis of mental disorders such as autism.

However, the study is unlikely to satisfy parent groups that have targeted the MMR vaccine as a possible source of their children's medical problems.

"This is not going to put the question to rest for parents whose perfectly normal children regressed after they received this vaccination," said Dawn Richardson, president of Parents Requesting Open Vaccine Education, an Austin-based group that includes about 3,500 families concerned about vaccine safety.

Such groups point to several smaller studies that have suggested that some children experience behavioral problems soon after receiving a measles, mumps and rubella vaccination at age 18 months. Autism experts have speculated that behavioral difficulties may become apparent at that age but be merely coincidental to the timing of vaccination shots.

"Maybe the vaccine is not the cause of autism disorders, but it could be the trigger," Ms. Richardson speculated. "Maybe it's not happening in Denmark, but we're saying there's something going on here in the U.S. with the children who are being vaccinated."

Barbara Loe Fisher, co-founder and president of another parent group, the National Vaccine Information Center, said a Danish study might not apply to American children.

"They are a genetically homogeneous people," Ms. Fisher said of the children in the Danish study. "And we are not."

Relevance in U.S.?

Dr. Greg Poland, a measles vaccine expert at the Mayo Clinic in Rochester, Minn., agreed that a study in one country might not always relate to people in another. However, he noted that many Americans are of Scandinavian descent.

While calling the new study "the single best epidemiological population study done on this issue," Dr. Poland also said that the findings were unlikely to convince people who have decided that vaccinations were harmful for their children.

"You can't change emotion or fear-based decisions with scientific data," Dr. Poland said. "It is exceedingly difficult for people not to assume cause and effect in situations like this." He heads the Mayo Vaccine Research Group and is a professor of medicine and infectious diseases at the Mayo Medical School.

The combination measles, mumps and rubella vaccine has been in use since 1988, leading some critics to link it to the growing incidence of autism in the United States and elsewhere. Studies have estimated there were two autism cases per 10,000 children ages 5 to 9 in the 1980s and early 1990s. By 2000, the incidence had grown to 10 cases per 10,000 children in the same age group.

However, Dr. Madsen and his colleagues noted in the new study that the autism increase in the United States and Denmark "occurred well after the introduction" of the MMR vaccine.

"Also, if there were any association between the MMR vaccination and autism, we would expect to see a rise in the diagnoses of autism in the time after vaccination," he said. "We did not see that."

E-mail sjacobson@dallasnews.com