Medical Readiness

Safety and Efficacy of the Anthrax Vaccine Gao ID: T-NSIAD-99-148 April 29, 1999

Some ailing Gulf War veterans believe that the military's anthrax vaccine is the cause of their unexplained health problems. Concerns about the safety and the efficacy of the vaccine have also been fueled by the Food and Drug Administration's discovery of problems at the facility manufacturing the vaccine. Studies of both the original anthrax vaccine (developed in the 1950s and first produced on a large scale by Merck) and a later version that was eventually licensed and given to U.S. troops (produced by the Michigan Department of Public Health using a different process) did not question the safety of the vaccine. However, depending on the type of monitoring system used, recorded reactions to the vaccine varied; short-term local or systemic reaction rates were higher under active monitoring systems than under passive ones. The vaccine's long-term safety has yet to be studied. A study done on the original vaccine concluded that it protected humans against Anthrax exposure through the skin. In the 1980s, DOD began testing the licensed vaccine in animals to see how well it protected against anthrax that was inhaled. These studies found that the licensed vaccine protected against some but not all strains of anthrax. Animal immunity, however, does not necessarily correspond to human immunity because the relationship between the level of immunity and protection rates has not been demonstrated. The Defense Department plans further research in this area. After FDA inspections of the facility manufacturing the vaccine uncovered numerous problems, the agency sent warning letters, including one in March 1997 announcing FDA's intention to revoke the facility's license. The facility closed its plant the following year and it is now being renovated. DOD is conducting supplemental testing of the lots of vaccine in its current inventory before distributing it.

GAO noted that: (1) the anthrax vaccine being given to U.S. military personnel was licensed in 1970; (2) before the vaccine was licensed, the vaccine and the manufacturing process were changed, creating a similar vaccine, produced by the Michigan Department of Public Health (MDPH), which was the one eventually licensed; (3) the safety study conducted before licensing used both the original vaccine and MDPH vaccine; (4) knowledge to date about the safety of the vaccine includes the results of the original study and a 1998 Department of Defense (DOD) study of 500 vaccine recipients; (5) while these studies identified varying rates of adverse reactions, they did not question the safety of the vaccine; (6) the long-term safety of the vaccine has not yet been studied; (7) prior to the time of the licensing, no human efficacy testing of the MDPH vaccine was performed; (8) however, a study was done on the efficacy of the original vaccine; (9) this study concluded that the vaccine provided protection to humans against anthrax penetrating the skin; (10) in the 1980s, DOD began testing the efficacy of the licensed vaccine on animals, focusing on its protection against inhalation anthrax; (11) DOD recognizes that correlating the results of animal studies to humans is necessary and told GAO that it is planning research in this area; (12) careful control of the manufacturing process is essential to ensure the quality of the product; (13) FDA inspections of the facility where the licensed vaccine was manufactured uncovered numerous problems; (14) the facility received warning letters from FDA, including one in March 1997, stating its intent to revoke the facility's license; (15) the facility closed its plant in 1998 and is now being renovated; (16) FDA requires the manufacturer to meet specifications for sterility, stability, purity, and potency; and (17) in addition to the lot release testing required by FDA, DOD is conducting supplemental testing of each lot from this plant before distributing the vaccine.

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