Medical ReadinessIssues Concerning the Anthrax Vaccine Gao ID: T-NSIAD-99-226 July 21, 1999
The Defense Department (DOD) announced in 1997 that all U.S. forces would be inoculated against anthrax, to protect against possible exposure on the battlefield. Questions have been raised, however, about the safety and the efficacy of the military's anthrax immunization program. Also, the Food and Drug Administration has cited manufacturing problems at the facility producing the vaccine. DOD recognizes that some of the concerns about the current vaccine might be mitigated through further testing and research. This testimony discusses (1) the extent to which the data support the need for six initial shots and an annual booster of the anthrax vaccine, (2) the relative merits and weaknesses of a passive surveillance system in determining adverse events, (3) the available data on differences in adverse reaction rates between men and women receiving the anthrax vaccine, and (4) the disadvantages of the current vaccine and the status of federal efforts to develop an improved anthrax vaccine.
GAO noted that: (1) no studies have been done to determine the optimum number of doses of the anthrax vaccine; (2) a study done during the early 1950s showed that animals could be protected against cutaneous anthrax using a three-dose schedule; (3) however, the number of doses was increased to six when three people who had received three doses of the vaccine were infected after exposure to anthrax; (4) in a study of the vaccine's human efficacy published in 1962, a six-dose schedule was used, and the researchers concluded that the vaccine provided protection against cutaneous exposure to anthrax; (5) in 1998, the manufacturer of the vaccine submitted a Food and Drug Administration (FDA) application to determine whether the number of shots in the initial schedule could be reduced from six to five; (6) although annual boosters are given, the need for this frequency and the amount of the booster dose has also not been evaluated; (7) Department of Defense (DOD) submits data on adverse events associated with the anthrax vaccine to the Vaccine Adverse Events Reporting System; (8) this system has several advantages; (9) it alerts FDA and Centers for Disease Control and Prevention (CDC) to previously unreported or unexpected increases in reported adverse events; (10) it is also a relatively affordable way to supplement the data collected on vaccines before they are licensed; (11) however, it is a passive surveillance system, which means that FDA and CDC must rely on vaccine recipients or their health care providers to report any adverse events after receiving the vaccine; studies show that adverse events are reported significantly less than they would be in an active surveillance system; (12) DOD has conducted three efforts to actively collect data on adverse reactions after servicemembers received the anthrax vaccine; (13) data from these efforts show that women reported twice the rate of adverse reactions than men for both local and systemic reactions; (14) a higher proportion of women than men reported making an outpatient medical visit after a vaccination, and more than twice the percentage of women reported that they missed one or more duty shifts after their vaccinations than did men; (15) the anthrax vaccine has several disadvantages; (16) the amount of protective antigen in the vaccine cannot be precisely measured, and it varies from lot to lot; and (17) also, the requirement for a six-dose schedule and annual booster shots, rather than a smaller number of doses, complicates the logistics of inoculating all of DOD's troops and increases the cost of the vaccine program.