Serum IgG antibody response to the protective antigen (PA) of Bacillus anthracis induced by anthrax vaccine adsorbed (AVA) among US military personnel

The seroconversion rates and geometric mean concentrations (GMC) of IgG anti-PA for stored sera from U.S. military personnel. immunized 3, 4, and 6 times with the U.S. licensed anthrax vaccine adsorbed were studied. Anti-PA IgG concentrations were measured by ELISA. All. 246 vaccines had low but detectable pre-immunization anti-PA IgG (GMC 1.83 mu g/ml). Three doses elicited a GMC of 59.92 mu g/mL and a seroconversion rate of 85.3%, four doses elicited a GMC of 157.44 mu g/mL and 67.9% and the sixth of 276.95 mu g/ml and 45.5%, respectively. The forth dose elicited 100% seroconversion compared to the pre-immunization level. These results should facilitate comparison between different immunization schedules and new vaccines. Published by Elsevier Ltd.