Questions & Answers
Anthrax - The Anthrax Vaccine
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Long Term Safety

  1. What do we know about the long-term safety of anthrax vaccine?
    Based on multiple objective sources of data, there are no known long-term side effects to anthrax vaccine.

  2. When people talk about "long term," what do they mean?
    There is no universal definition for "long term." When applied to vaccines, scientists may consider "long term" to be 6 months to 1 year or longer.

  3. I have heard people say that "no data has been collected more than 48 hours after anthrax vaccination." Is that statement true?
    No. Twenty safety studies of various types have been performed to assess anthrax vaccine. Several of these studies actively collected data for weeks or months after each vaccination:

    Brachman study: 24 and 48 hours after each dose

    Fort Bragg study: 1, 2, 3, 7, and 30 days after each dose

    Fort Detrick route-change study: 1, 2, 3, 7, and 30 days after each dose

    Tripler Army Medical Center study: 7 days or more after each dose

    Korea study: 2 weeks to 5 months after each dose

  4. I have heard people say "there are no long-term safety studies of anthrax vaccine." Is that statement true?
    No. Unlike the safety studies of single-dose vaccines, the 6-dose vaccination schedule for anthrax vaccine requires that individual vaccine recipients be observed for multiple months or years. Numerous studies have assessed the health of anthrax vaccine recipients over extended periods of time. The following list shows how much time elapsed after individual anthrax vaccine recipients received their first dose of anthrax vaccine:

    Vaccine Adverse Event Reporting System (VAERS) minutes to years

    Army Disability Discharge Study: 4.5 years

    Fort Detrick route-change study: 6 months

    Korea study: 6 months

    USAF vision study: at least 6 months

    Langley AFB study: at least 6 months

    Tripler Army Medical Center study: at least 1 year

    Brachman study: at least 1.5 years

    Inpatient/outpatient cohort study: at least 6 to 18 months

    Fort Detrick and US Army Medical Research Institute of Infectious Diseases (USAMRIID) 10 years or more

  5. Laboratory workers at Fort Detrick, Maryland, have been vaccinated against anthrax since the 1940s. What do we know about the long-term health of those workers?

    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.