elevations in levels of gamma globulins. These changes cannot necessarily be attributed to the vaccinations, as the workers studied were occupationally exposed to a number of virulent microbes. However, the studies did not report any clear adverse clinical consequences, such as neoplasms, amyloidosis, or autoimmune diseases.

This series of longitudinal clinical studies had several shortcomings. There was no comparison cohort and no random sampling of the employees. Therefore, the results may not be applicable to a broader population. Further, the outcomes may be due in part to the healthy worker effect, since the subjects were selected for the intensity and length of their immunization history, and individuals who left employment were not considered. Thus, the studies may have inadvertently focused on the most resilient individuals. Moreover, it would be difficult, if not impossible, to attribute adverse effects to any one vaccine, since the study subjects received multiple vaccines.

The committee reviewed summaries of data from the Vaccine Adverse Event Reporting System (VAERS).⁴ We did not, however, review the individual VAERS forms submitted by health care providers, people receiving the vaccination, family members, or others. VAERS data are useful as a sentinel for adverse events but are limited in their usefulness for assessing the rate or causality of adverse events since the information may be underreported, incomplete, or duplicative and may not always have been confirmed by medical personnel (IOM, 1994). From its inception in 1990 through July 1, 1999, there have been 215 VAERS reports regarding anthrax vaccination (Ellenberg, 1999). The majority of the reports describe local or systemic symptoms including injection site edema, injection site hypersensitivity, rash, headache, and fever. Twenty-two of the VAERS reports are considered serious events and were described as occurring (or being diagnosed) from 45 minutes to 41/2 months after the vaccination. The reports of serious events include severe injection site reactions, a widespread allergic reaction, a case of aseptic meningitis, an onset of lupus, an onset of inflammatory demyelinating disease, a diagnosis of bipolar disease, and two cases of Guillain-Barré syndrome (Ellenberg, 1999). FDA and CDC are responsible for monitoring the VAERS data to detect unusual trends and occurrences of adverse health effects. That monitoring assists the FDA and CDC in responding appropriately to adverse events. In recent congressional testimony, FDA stated that “the reports on the anthrax vaccine received thus far do not raise any specific concerns about the safety of the vaccine” (Ellenberg, 1999).

Additionally, there are a number of unpublished studies with data on the safety of the anthrax vaccine (Table 1). However, these studies are either ongoing or have not been published in the peer-reviewed literature, and they were therefore not considered in the committee’s conclusions regarding the strength of the evidence for associations with adverse health outcomes. In its full report, the committee uses these studies in determining its recommendations for future research directions. The studies are currently described

Front Matter (R1-R5)

An Assessment of the Safety of the Anthrax Vaccine: Letter Report (1-8)