Serum IgG antibody response to the protective antigen (PA) of Bacillus anthracis induced by Anthrax Vaccine Adsorbed (AVA) among U.S. military personnel

Abstract

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 vaccinees had low but detectable pre-immunization anti-PA IgG (GMC 1.83μg/mL). Three doses elicited a GMC of 60 μg/mL and a seroconversion rate of 85.3%, four doses elicited a GMC of 157 μg/mL and 67.9% and the sixth of 277 μg/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.