The present invention provides a means to broadly protect the military and the public from injury from biological warfare weapons, particularly infective agents such as anthrax. Beta (1,3)-glucans, particularly whole glucan particles, PGG-Glucan, and microparticulate glucan, provide general immune enhancement, thereby increasing the body's ability to defend against a wide variety of biological threats. Beta (1,3)-glucans have been shown to increase the resistance to infection by anthrax and other infectious organisms when administered before and after infection. The anti-infective mechanism of β(1,3)-glucan appears to involve stimulation of the innate immune system through increased cytokine release and CR3 receptor activation. Beta (1,3)-glucan is pharmaceutically stable, relatively compact, and can also be used without significant side effects. Beta (1,3)-glucan can also enhance the effectiveness of other medical countermeasures such as antibiotics, vaccines, and immune antibodies.