http://www.cnn.com/2009/HEALTH/04/02...ate/index.html
Do vaccines cause autism?
In 1998, a theory emerged that the measles-mumps-rubella (MMR) vaccine caused autism, the theory being that the vaccine lingered in the gut, causing gastrointestinal problems, and that those GI problems led to autism.
A few years later, the very small study that was the basis of this theory was debunked and discredited. However, this did not quash the belief among many parents that vaccines caused autism, leading them to stop or delay immunizing their children.
Since the first World Autism Awareness Day last year, a couple of studies and a major court decision declared definitively that vaccines do not cause autism.
In September, researchers in the United States and Europe re-created the original 1998 study, even using one of the same laboratories to analyze their results. The study authors concluded that "no evidence" linked the MMR vaccine to autism or the GI problems.
While many experts said this study is conclusive and "puts the issue to rest," some groups that hold to the belief vaccines are the cause of autism called the research flawed.
Another study, published in the March 2009 issue of Pediatrics, provided an explanation of why the MMR vaccine does not cause GI problems and autism.
Daniel Campbell, a researcher at Vanderbilt University, suggested that he has found a reasonable explanation for why many children also have GI problems. According to his research, a genetic variation of a protein called MET contributes to both autism and GI problems, rather than GI problems causing autism.
In addition, a decision inside a courtroom rather than a laboratory drew the conclusion that the vaccines do not cause autism.
On February 12, a special vaccine court ruled in three test cases, representing more than 5,000 families, that the "combination of the thimerosal-containing vaccines and the MMR vaccine are not casual factors in the development of autism."
It's probably still too early to tell whether these rulings changed anyone's opinions. "I don't think they were important from the standpoint of changing the minds of those with firmly held beliefs regarding vaccines," said Dr. Bryan King, director of child psychiatry at Seattle Children's Hospital. He said that it will not be until we find credible causes for autism that people can leave this debate behind.
"We still support research that would potentially identify small groups with underlying medical or genetic conditions who may be more vulnerable to the adverse effects of vaccines," said Dr. Geraldine Dawson, the chief science officer of Autism Speaks, the nation's largest advocacy group.
"For the vast majority of kids, vaccines are safe and we support vaccine programs," Dawson said, adding that more research into vaccines is needed.