1999). More than 400 members of the military who refused to accept vaccination with AVA have left military service voluntarily or involuntarily (Weiss, 2001), and mandatory vaccination against anthrax is reported to have been an important factor to some Air National Guard and Air Force Reserve personnel when making their decision to leave military service or move to inactive status (GAO, 2000).

As described in Chapter 2, the symptoms associated with vaccination against anthrax reported by witnesses at congressional hearings and directly to this Institute of Medicine (IOM) committee included fever, headache, malaise, swelling, joint pain, and tinnitus. Several witnesses also reported conditions that they ascribed to receipt of the anthrax vaccine, including hypogonadism; Stevens-Johnson syndrome, which affected their vision as well as their skin; and fatal aplastic anemia.

Recent reports from an IOM committee examining the potential health effects of agents to which Gulf War veterans may have been exposed concluded that receipt of AVA was associated with transient acute local and systemic effects (e.g., redness, swelling, and fever) but that the available evidence was “inadequate/insufficient” to determine whether any association with long-term adverse health effects exists (IOM, 2000a,b). That committee restricted its review, however, to the limited number of published studies. Since those IOM reports were completed, results of new Department of Defense (DoD) studies of health effects following vaccination with AVA have become available. The present report examines these new findings and reviews the older data.

IDENTIFYING VACCINE-RELATED ADVERSE EVENTS

An adverse event is an undesirable health outcome that follows a given exposure, as to a vaccine, but for which a causal relationship with the exposure may or may not have been established. If a causal relationship can be determined, adverse events can also be referred to as adverse effects or adverse reactions.

Determining whether receipt of a vaccine has caused a subsequent adverse event can be difficult (Chen, 2000; Ellenberg and Chen, 1997; IOM, 1997). Several IOM committees have had the task of evaluating evidence regarding suspected links between various vaccines and particular adverse events (IOM, 1991, 1994a,b, 2000b, 2001). The available data indicate that some vaccines are associated with rare but serious adverse effects (IOM, 1991, 1994a). In other cases, however, the available evidence does not support the hypothesized associations between adverse events and vaccination (IOM, 1994a, 2001). Several factors involved in assessment of whether a vaccine is associated with adverse events are reviewed here.



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