The antibody profile during and after the six-dose primary vaccination series with anthrax vaccine adsorbed (AVA, BiothraxTM)was characterized in 86 human volunteers. Ninety-three percent of recipients developed IgG antibodies to Bacillus anthracis protective antigen (PA) after two doses, and 100% were seropositive after dose #3. Geometric mean concentrations (GMC) of IgG to PA measured before and after each dose were significantly lower after injection #3 (peak GMC = 146.65 micrograms ...