various periods following inoculation, with some study reports not indicating the lengths of such periods. Thus, some adverse event rates apply to the first 24 to 48 hours postimmunization, whereas others may apply to the period from days to weeks following vaccination. Third, studies differ in their methods of ascertaining the presence of adverse events. Some studies used active surveillance to identify local and systemic reactions, with all recipients monitored on a regular basis at specified intervals. Other studies relied on passive surveillance, with vaccine recipients deciding whether an adverse event had occurred and whether to report that event. Fourth, the anthrax vaccine formulation was not constant across studies, and in some studies the anthrax vaccine was administered in combination with other vaccines. In addition, studies differed in the number of anthrax vaccine doses given. Finally, the adverse event rates reported were sometimes based on the number of doses administered and were sometimes based on the number of persons vaccinated. It should be noted that the same considerations affect the evaluation of safety for other vaccines as well.1 The summary of findings presented below and in Tables 6-1 to 6-4 (referred to as the adverse events tables) should be read with the foregoing considerations in mind.

AD HOC STUDIES

Studies of Health Effects with Immediate Onset

Randomized Controlled Trials

Brachman Study Brachman and colleagues (1962) conducted the only randomized, placebo-controlled trial of the efficacy of a protective antigen anthrax vaccine. Information on events of immediate onset following immunization is presented here; information on the efficacy of the vaccine is reported in Chapter 3. The vaccine studied was not AVA but was an earlier formulation produced from the R1-NP strain of anthrax (see Chapter 7 for more details). The study was carried out from January 1955 through March 1959 in four mills in the eastern United States that processed raw imported goat hair, which was commonly contaminated with anthrax spores.

The worker population eligible for the study included 1,249 men and women with no history of prior anthrax infection. The numbers of study

1  

An international effort is under way to standardize case definitions of many of the adverse events that can follow vaccination. The Brighton Collaboration was launched in the autumn of 2000 and has now developed several definitions in draft form (http://brightoncollaboration.org/index.cfm).



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