Assessing the safety of anthrax immunization in US Army aircrew members via physical examination

Anthrax in weaponized form is the bioterrorism agent of most concern. Questions raised about the safety of the anthrax vaccine can be addressed by comparing immunized and unimmunized people in population-based studies.

A retrospective evaluation of data from periodic physical examinations collected on anthrax-immunized and -unimmunized US Army aircrew members between 1998 and 2005 was performed to evaluate the safety of anthrax immunization. Mean changes in variables found on physical examination and laboratory analysis were compared by use of t tests. Multiple linear regression predicted change in outcome from baseline characteristics.

We compared 6,820 immunized subjects and 4,145 unimmunized controls based on US Army aircrew physical examination and screening laboratory tests. No association between anthrax immunization and a clinically relevant change in a tested physiologic parameter was detected.

No attributable risk of anthrax immunization was observed in this group of Army aircrew members.