The current dose of the licensed tetravalent A/C/Y/W135 polysaccharide vaccine contains 50 μg of each polysaccharide component. During the 1980’s, researchers from the Walter Reed Army Institute of Research (WRAIR) did extensive works on the immunogenicity of meningococcal polysaccharide vaccines in adults. A first study performed by Griffiss et al. demonstrated that doses of 5 μg of group Y and group W135 polysaccharides were as effective as doses of 50 μg in inducing production of bactericidal antibody amounts correlating with functional immunity (Griffiss et al. Mil Med 1985; 150: 529-33). A second study concluded that doses of 7.5 μg (Y and W) and 15 μg (A and C) were sufficient to induce equivalent binding and bactericidal antibody responses as 50 μg (Griffiss et al. Infect Immun 1982; 37: 205-8). In a more recent study from Granoff et al., 1/50 (1 mcg) of the ordinary dose of tetravalent A/C/Y/W135 vaccine was given (Granoff et al. J Infect Dis 1998; 178: 870-4). The antibody responses to A and C have been measured, and this low dose was sufficient to mount a C response in most of the subjects, but the dose was less effective in eliciting a response to A. The antibody responses to W135 and Y were not reported.