Disclosed is an immunological composition comprising a mixture of four distinct and separately made protein-capsular polysaccharide conjugates, wherein the first conjugate comprises purified Neisseria meningitidis capsular polysaccharide of serogroup W-135 conjugated to a carrier protein, the second conjugate comprises purified N. meningitides capsular polysaccharide of serogroup Y conjugated to a carrier protein, the third conjugate comprises purified N. meningitidis capsular polysaccharide of serogroup A conjugated to a purified carrier protein, and the fourth conjugate comprises purified N. meningitidis capsular polysaccharide of serogroup C conjugated to a carrier protein, wherein the immunological composition elicits, in children less than two years of age, a primary serum IgG response and a serum bactericidal antibody response to each of the N. meningitidis serogroups A, C, W-135 and Y capsular polysaccharides, wherein said serum bactericidal antibody response is higher than that elicited by the licensed, unconjugated, tetravalent A, C, W-135 and Y meningococcal capsular polysaccharide vaccine, and further wherein the immunological composition is capable of eliciting a booster anamnestic IgG response to each of the N. meningitidis serogroups A, C, W-135 and Y capsular polysaccharides.
