[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.

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Yet despite all evidence to the contrary, the number of parents who blame thimerosal for their children's autism has only increased. And in recent months, these parents have used their numbers, their passion and their organizing skills to become a potent national force. The issue has become one of the most fractious and divisive in pediatric medicine.

"This is like nothing I've ever seen before," Dr. Melinda Wharton, deputy director of the National Immunization Program, told a gathering of immunization officials in Washington in March. "It's an era where it appears that science isn't enough."

Parents have filed more than 4,800 lawsuits - 200 from February to April alone - pushed for state and federal legislation banning thimerosal and taken out full-page advertisements in major newspapers. They have also gained the support of politicians, including Senator Joseph I. Lieberman, Democrat of Connecticut, and Representatives Dan Burton, Republican of Indiana, and Dave Weldon, Republican of Florida. And Robert F. Kennedy Jr. wrote an article in the June 16 issue of Rolling Stone magazine arguing that most studies of the issue are flawed and that public health officials are conspiring with drug makers to cover up the damage caused by thimerosal.

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In 2000, a group of parents joined together to found SafeMinds, one of several organizations that argue that thimerosal is that environmental culprit. Their cause has been championed by politicians like Mr. Burton.

"My grandson received nine shots in one day, seven of which contained thimerosal, which is 50 percent mercury as you know, and he became autistic a short time later," he said in an interview.

In a series of House hearings held from 2000 through 2004, Mr. Burton called the leading experts who assert that vaccines cause autism to testify. They included a chemistry professor at the University of Kentucky who says that dental fillings cause or exacerbate autism and other diseases and a doctor from Baton Rouge, La., who says that God spoke to her through an 87-year-old priest and told her that vaccines caused autism.

Also testifying were Dr. Mark Geier and his son, David Geier, the experts whose work is most frequently cited by parents.

Trying to Build a Case

Dr. Geier has called the use of thimerosal in vaccines the world's "greatest catastrophe that's ever happened, regardless of cause."

In 2003, spurred by parents' demands, the C.D.C. asked the Institute of Medicine, an arm of the National Academy of Sciences and the nation's most prestigious medical advisory group, to review the evidence on thimerosal and autism.

In a report last year, a panel convened by the institute dismissed the Geiers' work as having such serious flaws that their studies were "uninterpretable." Some of the Geiers' mathematical formulas, the committee found, "provided no information," and the Geiers used basic scientific terms like "attributable risk" incorrectly.

In contrast, the committee found five studies that examined hundreds of thousands of health records of children in the United States, Britain, Denmark and Sweden to be persuasive.

A study by the World Health Organization, for example, examined the health records of 109,863 children born in Britain from 1988 to 1997 and found that children who had received the most thimerosal in vaccines had the lowest incidence of developmental problems like autism.

Another study examined the records of 467,450 Danish children born from 1990 to 1996. It found that after 1992, when the country's only thimerosal-containing vaccine was replaced by one free of the preservative, autism rates rose rather than fell.

In one of the most comprehensive studies, a 2003 report by C.D.C. scientists examined the medical records of more than 125,000 children born in the United States from 1991 to 1999. It found no difference in autism rates among children exposed to various amounts of thimerosal.

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