Human immune response to various doses of group Y and W135 meningococcal polysaccharide vaccines.

A divalent vaccine containing equal weights of Neisseria meningitidis group Y and group W135 capsular polysaccharides was inoculated subcutaneously into groups of 32 military recruit volunteers at doses of 10, 25, 50, and 100 micrograms in 10-microliter/microgram volumes. At 4 weeks, the two higher doses induced significantly greater binding antibody responses than did the two lower doses. Differences in response were not found between the two higher doses or between the two lower doses. An additional 32 volunteers received a dose of 25 micrograms in a 20-microliter/microgram volume. Binding antibody response to this vaccine did not differ from the response to doses of 10 and 25 microgram in 10-microliter/microgram volumes. In contrast, bactericidal antibody responses did not differ among doses. Bactericidal antibody was induced in 100% of individuals with low (greater than 4 log2) preexisting serum bactericidal activity, regardless of dose. Bactericidal antibody nonresponse was restricted to individuals with high preexisting serum bactericidal titers. The discrepant dose response between binding and bactericidal antibody resulted from the induction of nonlytic antibody by the higher doses. We conclude that there are no advantages to doses in excess of 5 micrograms of these two chemically similar polysaccharides for the target population of young adult military recruits.