Simpsonwood, thimerosal, and vaccines (I)

Robert F. Kennedy Jr. claims that the transcript of the CDC's Scientific Review of Vaccine Safety Datalink Information (hereafter, Simpsonwood) is definitive proof of a government/industry conspiracy to conceal the health effects of thimerosal in vaccines.

The 286-page transcript doesn't come close to vindicating Kennedy's grandiose claims. (Available here.) The proceedings are interesting in their own right. I'll be discussing them at much greater length over the next couple of days.

The real moral of this story is that retrospective administrative database studies are highly overrated. Regardless of the risks associated with thimerosal, or lack thereof, the CDC/VSD study could scarcely have raised issues for discussion, let alone shed light on any potential causal relationship between thimerosal and autism. A retrospective administrative database analysis is just too crude a tool for the job.

Before I get into the research itself, let me give you some background on the nature and scope of the meeting. The conference was held at the Simpsonwood Retreat Center in Norcross, Georgia on June 7-8, 2000. It was sponsored by National Immunization Program (NIP) of Centers for Disease Control (CDC). The CDC and the Vaccine Safety Datalink (VSD) collaborated on a major retrospective administrative database study.

Prominent academics and clinicians, representatives from the CDC, the FDA, European regulatory bodies, the American Academy of Pediatrics, and representatives of the major vaccine manufacturers were invited. The group was asked to review the CDC/VSD data in order to make recommendations to the the CDC's Advisory Committee on Immunization Practices (ACIP). ACIP is the 15-member NIP committee that drafts the CDC's written recommendations for pediatric and adult vaccination schedules (ACIP homepage). Five voting members of ACIP attended the Simpsonwood meeting. These delegates simultaneously constituted the initial ACIP working group on thimerosal and vaccination.

Topline summary: The experts met, they reviewed the data, they found some correlations, they explained to each other why the data were hopelessly confounded, they agreed that the study in no way ruled out possible health effects of thimerosal, and some of the more politically savvy participants wondered aloud whether these inconclusive results might get them sued.

To be continued.