The antigenicity of cholera vaccine prepared in fluid medium.

Cholera vaccine prepared in a chemically defined fluid medium (containing tyrosine, asparagine, glycine, and inorganic salts) was compared antigenically in mice with vaccines prepared by standard methods. The mean LD50 for normal mice was 108 ± 9.1 V. comma of the strain employed for challenging. Both vaccines afforded a high degree of protection. Mice immunized with bivalent (Ogawa and Inaba) Standard vaccine had a mean LD50 of 40.0 ± 4.7 million V. comma. Mice protected by bivalent fluid-prepared vaccine had a mean LD50 of 32.7 ± 6.0 million V. comma. The difference is not statistically significant. Vaccines prepared in fluid medium were relatively unstable.