Provided is an immunogenic composition comprising 13 different polysaccharide-protein conjugates. Each of the conjugates comprises a capsular polysaccharide prepared from a different serotype Streptococcus pneumoniae conjugated to a carrier protein, that is, 12 serotypes selected from the group consisting of 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F and 23F and serotype 22F or 33F. The immunogenic composition formulated into a vaccine comprising an aluminum-based adjuvant increases coverage with respect to pneumococcal diseases in infants and children.