At Fort Detrick, Maryland, 99 laboratory workers were evaluated 10 to 20 years after receiving anthrax vaccine. Most of these workers received 150 to 200 doses of various vaccines (including anthrax vaccine); some received more than 300 such injections during their tenure at Fort Detrick. This study "failed to produce evidence that development of neoplasms, amyloidosis, or autoimmune diseases was associated with the vaccine dosages and frequencies used at Fort Detrick. The authors concluded "These data and the accompanying evaluation of an intensively immunized population provide evidence that no obvious adverse effects result from repeated immunization." The first report of this group of vaccine recipients was published in the Bulletin of the Johns Hopkins Hospital in 1958. Two follow-up reports were published in the Annals of Internal Medicine in 1965 and 1974.

An extension of this long-term study is underway at the U.S. Army Medical Research Institute for Infectious Diseases (USAMRIID) to determine, in even greater detail, whether people who received multiple vaccines, including anthrax vaccine, during their past employment at Fort Detrick demonstrated any adverse health effects over the long term. More than 1,500 employees have been followed annually there. In a case-control study begun in 1996, vaccinated and unvaccinated volunteers have been enrolled. All volunteers signed an informed-consent document. The study methods include a 9-page health history questionnaire, extensive blood tests and urinalysis. The questionnaire queries mental and physical conditions of the volunteers, as well as the health of their offspring. Study end points include symptoms, symptom complexes (including symptoms reported by veterans of the Persian Gulf War), diseases, and abnormal laboratory and urine tests. Study subjects will be compared to two to three race-, gender-, and age-matched control subjects to determine if any long-term medical effects exist among this unique group of study subjects. Analysis of the data from the extensive health history questionnaire and numerous laboratory tests are currently in progress. No unexplained symptoms due to repeated doses of anthrax or other vaccines have been found. From this and other monitoring, no patterns of delayed side effects to anthrax vaccine have been found. Monitoring continues.

White CS III, Adler WH, McGann VG. Repeated immunization: Possible adverse effects: Reevaluation of human subjects at 25 years. Annals of Internal Medicine 1974; 81:594-600.