[p. 7-8]Discussion on the link between vaccines and autism

Mr. Albert Enayati, a meeting attendee, asked about the association between vaccines and autism. He noted that an overwhelming majority of parents at a recent meeting felt strongly that thimerosal (a preservative used in vaccines that contains ethyl mercury) caused autism in their children.

Dr. Alexander acknowledged that this is a topic that has received a tremendous amount of attention. He cited several separate and independent efforts--including those by the Institute of Medicine (IOM) and the United Kingdom\ufffds Committee on Safety of Medicine--that have pointed to the lack of support for an association between autism and the MMR vaccine. At the same time, a number of groups are trying to address this issue. These include the CPEAs\ufffd work in conjunction with the CDC discussed above. Another effort involves the National Children\ufffds Study (NCS), a longitudinal cohort study of environmental effects on child health and development, which was mandated when the Children's Health Act of 2000 was signed into law, laying the groundwork for a 30-year study to follow 100,000 children from before birth to adulthood. This effort, led by the NICHD, CDC, and EPA, together with other NIH Institutes and Federal agencies, will include data on environmental exposures during pregnancy and postnatally to examine environmental agents including vaccines. This study might be able to address this question of the link between MMR vaccine and autism as well.

Concerns about the ability of the NCS to answer the vaccine-autism link were raised. Dr. Jos\ufffd Cordero clarified that the MMR vaccine does not contain thimerosal. Studies can only be done in a retrospective fashion because currently available vaccines do not contain or contain only trace amounts of thimerosal. Thus, the NCS with its prospective, longitudinal design may not be able to definitively address the vaccine-autism link. Ms. Barbara Loe Fisher, a meeting attendee and President of the National Vaccine Information Center, stated that the epidemiological design of the NCS is insufficient to address the vaccine-autism link and asked if more in-depth studies are planned. Dr. Alexander noted that up to 10-20 percent of children do not receive vaccines; the size of the study may allow for adequate comparisons of the impact of vaccines. He also said that the NCS is an observational study and plans for in-depth studies such as brain imaging have not been determined.

Dr. Gordon cautioned against an over-focus on vaccines. The cause or causes of autism have yet to be determined, and there is an extremely large number of possibilities. He suggested that the public needs to be educated about the plausibility of reported findings and about how much investigative weight to apply to such findings. Perhaps criteria can be agreed upon, by public groups as well as by scientific ones, by which reported findings could be evaluated.