Immunological Studies of Anthrax

Abstract

Summary Levels of resistance to challenge with spores of a virulent strain of Bacillus anthracis were measured by means of an immunity index. The immunizing effect of protective antigen alone produced a level of resistance approximately 1000-fold greater than that of controls. The effect of protective antigen and a supplemental injection of live vaccine was 100,000,000-fold. Live vaccine alone produced only a 10- to 15-fold increase in resistance.