Clearly, plenty of theories connect the MMR and autism -- and plenty of researchers are busy presenting their findings. At present, though, there is no conclusive evidence that live-virus vaccines actually cause autism. The CDC, the Institute of Medicine and other major research institutions studied the research conducted to date, and concluded that there is no evidence to support the connection.
First, they say, the original 1998 Wakefield stufy was fatally flawed. "For example," they say, "the study was very small, involving only 12 children. This is too few cases to make any generalizations about the causes of autism. In addition, the researchers suggested that MMR vaccination caused bowel problems in the children, which then led to autism. However, in some of the children studied, symptoms of autism appeared before symptoms of bowel disease."
The CDC also cites a series of larger statistical studies carried out in the UK and Scandinavia which show that the number of children with autism did not spike when the combined MMR vaccine was introduced. In addition, the UK study found that "the onset of "regressive" symptoms of autism did not occur within 2, 4, or 6 months of receiving the MMR vaccine." Yet more studies are underway. One, which involves a collaboration among the NICHD, other NIH Institutes, the CDC, the Environmental Protection Agency, and other federal agencies, will involve a large, long-term study of the effects of the environment on children's health. According to the NICHD website: "This study will follow 100,000 children from before birth to age 20, to track growth and development, and well as study genetic blueprints and environmental factors. Researchers hope to develop theories about whether environmental influences, such as pollutants or vaccines, can cause abnormal development, such as autism, asthma, or other childhood disorders that have shown dramatic increase."
Neither the CDC nor proponents of the vaccine theories think that parents should avoid vaccines. Clearly, vaccines have saved untold lives, and will continue to do so. but some groups that worry about the safety of live-virus vaccines think they should be given one at a time over a period of months, rather than all at once through combined injections. The CDC has conducted research which seems to show that there is no causal link between multi-virus injections and autism, and their information website states that "there is no published scientific evidence showing that there is any benefit to separating the combination MMR vaccine into three individual shots." Concerned parents should talk with their pediatricians about this issue.
Sources: CDC Factsheet on MMR and Autism
Thoughtful House FAQs
"Immune system response may cause autism" in the University of Michigan Record, November 1998.{p] "The Age of Autism: Pox" in Science Daily website, May 2006.
No comments:
Post a Comment