Provided are mixed carrier, multivalent pneumococcal conjugate compositions comprising 20 different pneumococcal capsular polysaccharide-protein conjugates, wherein each of the conjugates includes a capsular polysaccharide from a different serotype of Streptococcus pneumoniae conjugated to either tetanus toxoid or CRM197, wherein the Streptococcus pneumoniae serotypes are selected from 1, 3, 4, 5, 6A, 6B, 7F, 8, 9V, 10A, 11A, 12F, 14, 15B, 18C, 19A, 19F, 22F, 23F, and 33F, wherein two of the capsular polysaccharides are conjugated to tetanus toxoid and the remaining capsular polysaccharides are conjugated to CRMig7, and wherein the two capsular polysaccharides that are conjugated to tetanus toxoid are selected from the group consisting of serotypes 1, 3, and 5. Also provided are methods of producing the mixed carrier, multivalent pneumococcal conjugate compositions and methods of using the same for prophylaxis against Streptococcus pneumoniae infection or disease in a subject.