Human immunity to the meningococcus. V. The effect of immunization with meningococcal group C polysaccharide on the carrier state.

Purified meningococcal polysaccharides were administered to army recruits. No adverse reactions were observed in 145 men who received group C polysaccharide, and in 53 men who were injected with group A polysaccharide. Hemagglutinating and bactericidal activity developed in the sera of all individuals with the exception of two recruits injected with A polysaccharide. During the 6 wk period of observation, the proportion of unvaccinated recruits who acquired group C meningococci in the three companies studied was 38, 42, and 69 per cent. A significantly lower proportion of the individuals vaccinated with group C polysaccharide acquired group C meningococci; 4.6, 24, and 31 per cent respectively.