With these vaccines, scientists recognize that each successive dose builds on the effect of earlier doses. Later doses build progressively higher levels of disease-fighting antibodies in the bloodstream, like climbing steps on a ladder or a staircase towards full protection. Like other vaccines, each of the initial doses of anthrax vaccine stimulates increasingly higher amounts of anti-anthrax antibodies. Next, these soldiers received one additional dose of anthrax vaccine . A high antibody-response rate after a single booster dose of a vaccine shows that the immune system remembers the previous vaccinations, even if antibodies were not detected just before the booster dose.
Antibody responses to anthrax vaccine require careful interpretation.
The concentration of anti-anthrax antibodies that protects humans from anthrax disease is not precisely known.