Group B

1. An immunogenic composition comprising polysaccharide-protein conjugates, wherein the conjugates comprise capsular polysaccharides from group B streptococcus (GBS) serotypes Ia, Ib, II, III, IV and V, and wherein at least one of the capsular polysaccharides has a sialic acid level of greater than about 60%.

2. The immunogenic composition of claim 1 , wherein the GBS capsular polysaccharides have at least about 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, or 0.95 mM sialic acid per mM of polysaccharide.

3. The immunogenic composition of claim 1 , wherein the GBS capsular polysaccharides have a molecular weight of between about 5 kDa and about 1,000 kDa; between about 25 kDa and about 750 kDa; between about 25 kDa and about 400 kDa; between about 25 kDa and about 200 kDa; or between about 100 kDa and about 400 kDa.

4. The immunogenic composition of claim 1 , wherein the molecular weight of the conjugate is between about 300 kDa and about 20,000 kDa; between about 1,000 kDa and about 15,000 kDa; or between about 1,000 kDa and about 10,000 kDa.

5. The immunogenic composition of claim 1 , wherein the capsular polysaccharides are between about 0% and about 40% O-acetylated.

6. The immunogenic composition of claim 1 , wherein the capsular polysaccharides are less than about 5%, less than about 4%, less than about 3%, less than about 2%, or less than about 1% O-acetylated.

7. The immunogenic composition of claim 1 , wherein the capsular polysaccharides have at least about 0.1, 0.2, 0.3, 0.35 or about 0.4 mM O-acetate per mM saccharide repeating unit.

8. The immunogenic composition of claim 1 , wherein the protein in each conjugate is CRM197 or tetanus toxoid.

9. The immunogenic composition of claim 8 , wherein the protein is CRM197.

10. The immunogenic composition of claim 1 , wherein the composition further comprises a pharmaceutically acceptable excipient, buffer, stabilizer, adjuvant, a cryoprotectant, a salt, a divalent cation, a non-ionic detergent, an inhibitor of free radical oxidation, a carrier, or a mixture thereof.

11. The immunogenic composition of claim 10 , further comprising a buffer.

12. The immunogenic composition of claim 11 , wherein the buffer is selected from the group consisting of HEPES, PIPES, MES, Tris (trimethamine), phosphate, acetate, borate, citrate, glycine, histidine and succinate.

13. The immunogenic composition of claim 10 , further comprising a surfactant.

14. The immunogenic composition of claim 13 , wherein the surfactant is selected from the group consisting of polyoxyethylene sorbitan fatty acid esters, polysorbate-80, polysorbate-60, polysorbate-40, polysorbate-20, and polyoxyethylene alkyl ethers.

15. The immunogenic composition of claim 10 , further comprising an excipient.

16. The immunogenic composition of claim 15 , wherein the excipient is selected from the group consisting of starch, glucose, lactose, sucrose, trehalose, raffinose, stachyose, melezitose, dextran, mannitol, lactitol, palatinit, gelatin, malt, rice, flour, chalk, silica gel, sodium stearate, glycerol monostearate, talc, glycine, arginine, lysine, sodium chloride (NaCl), dried skim milk, glycerol, propylene glycol, water, and ethanol.

17. The immunogenic composition of claim 10 , further comprising an adjuvant.

18. The immunogenic composition of claim 17 , wherein the adjuvant is an aluminum-based adjuvant or QS-21.

19. The immunogenic composition of claim 10 , further comprising a buffer, a surfactant, an excipient, and optionally an adjuvant, wherein the conjugate is buffered to a pH of about 6.0 to about 7.0.

20. The immunogenic composition of claim 19 , wherein the conjugate comprises a dose of about 5 mcg/ml to about 50 mcg/ml.

21. The immunogenic composition of claim 19 , wherein the conjugate is lyophilized, optionally in the presence of at least one excipient.

22. The immunogenic composition of claim 21 , wherein the at least one excipient is selected from the group consisting of starch, glucose, lactose, sucrose, trehalose, raffinose, stachyose, melezitose, dextran, mannitol, lactitol, palatinit, gelatin, malt, rice, flour, chalk, silica gel, sodium stearate, glycerol monostearate, talc, glycine, arginine, lysine, sodium chloride (NaCl), dried skim milk, glycerol, propylene glycol, water, and ethanol.

23. The immunogenic composition of claim 22 , wherein the at least one excipient is sucrose.

24. The immunogenic composition of claim 21 , further comprising an additional excipient.

25. The immunogenic composition of claim 24 , wherein the additional excipient is mannitol or glycine.

26. An immunogenic composition comprising polysaccharide-protein conjugates from group B streptococcus (GBS) serotype IV and at least five additional serotypes selected from the group consisting of serotypes Ia, Ib, II, III, V, VI, VII, VIII, and IX.

27. An immunogenic composition comprising polysaccharide-protein conjugates comprising at least six GBS capsular polysaccharides selected from the group consisting of serotypes Ia, Ib, II, III, IV, V, VI, VII, VIII, and IX.

28. The immunogenic composition of claim 27 , wherein the composition comprises GBS capsular polysaccharide serotype V.

29. The immunogenic composition of claim 28 , wherein the composition does not have immune interference.

30. An immunogenic composition according to claim 26 or 27 , wherein the protein is CRM197 or tetanus toxoid.

31. An immunogenic composition according to claim 30 , wherein the protein is CRM197.

32. An immunogenic composition comprising six distinct polysaccharide-protein conjugates, wherein:

(i) the polysaccharide in each of the six conjugates is a capsular polysaccharide selected from the group consisting of group B streptococcus (GBS) serotypes Ia, Ib, II, III, IV, and V;

(ii) the protein in each conjugate is CRM197; and

(iii) the capsular polysaccharide in each conjugate has a sialic acid level of greater than about 60%.