Anthrax Vaccine:

Safety and Efficacy Issues

T-NSIAD-00-48: Published: Oct 12, 1999. Publicly Released: Oct 12, 1999.

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Kwai-Cheung Chan
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Pursuant to a congressional request, GAO discussed the results of its ongoing examination of the safety and efficacy of the anthrax vaccine, focusing on the: (1) need for a six-shot regimen and annual booster shots; (2) long- and short-term safety of the vaccine; (3) efficacy of the vaccine; (4) extent to which problems the Food and Drug Administration (FDA) found in the vaccine production facility in Michigan could compromise the safety, efficacy, and quality of the vaccine; and (5) effects of the anthrax vaccine on children, pregnant women or lactating women.

GAO noted that: (1) no studies have been done to determine the optimum number of doses of the anthrax vaccine; (2) although annual boosters are given, the need for a six-shot regimen and annual booster shots have not been evaluated; (3) the long-term safety of the licensed vaccine has not been studied; (4) however, the Department of Defense (DOD) is designing studies to examine the vaccine's long-term effects; (5) data on the prevalence and duration of short-term reactions to the vaccine are limited but suggest that women experience a higher rate of adverse reactions than do men; (6) FDA's system for collecting data on adverse events associated with the vaccine, which DOD uses, relies on vaccine recipients or their health care providers to report adverse events; (7) studies have shown that such systems may not accurately reflect the incidence of events due to underreporting; (8) however, data from two recent DOD efforts to identify the prevalence of adverse events associated with anthrax vaccine show that a higher proportion of women reported both local and systemic reactions to the vaccine than their male counterparts; (9) in addition, more than twice the proportion of women reported that they missed one or more duty shifts after their vaccinations than did males; (10) a study on the efficacy of the earlier vaccine concluded that it provided protection to humans against anthrax penetrating the skin but did not provide information to determine the effectiveness against inhalation anthrax; (11) in the 1980's, DOD began testing the efficacy of the licensed vaccine in animals, focusing on its protection against inhalation anthrax; (12) the studies showed that the vaccine protected some animals against inhalation anthrax; (13) however, the level of protection varied for different species and the results cannot be extrapolated to humans; (14) DOD recognizes that correlating the results of animal studies to humans is necessary and told GAO that it is planning research in this area; (15) DOD also plans to develop a second generation anthrax vaccine and, as part of this effort, will need to address whether strains of deliberately engineered or naturally occurring anthrax can overcome the protective immunity of such a vaccine; and (16) FDA's inspections of the vaccine production facility in 1997 and 1998 found a number of deficiencies.

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