Modified capsular saccharides comprising a blocking group at a hydroxyl group position on at least one of the monosaccharide units of the corresponding native capsular saccharide, wherein the blocking group is of the formula (Ia) or (Ib): -O-X-Y (Ia) or -O-R 1 (Ib) wherein X is C(O), S(O) or SO 2 ； Y is NR 1 R 2 or R 3 ； R 1 is C 1-6 alkyl substituted with 1, 2 or 3 groups independently selected from hydroxyl, sulphydryl and amine； R 2 is H or C 1-6 alkyl； and R 3 is C 1-6 alkyl； processes for modifying a capsular saccharide with the blocking groups； saccharide-protein conjugates comprising the modified capsular saccharide； processes for making the saccharide-protein conjugates, pharmaceutical compositions comprising the modified capsular saccharides and/or saccharide-protein conjugates； and methods and uses of the same.
