An immunogenic composition comprising: (a) a glycan conjugate including a carrier and one or more glycans, and optionally (b) an adjuvant; wherein each of the one or more glycans is conjugated with the carrier through a linker having the formula: wherein: X 1 is selected from -OR, wherein R is selected from an oxygen protecting group, optionally substituted C 1-10 alkyl, optionally substituted aryl, optionally substituted acyl, and optionally substituted imidoyl; or X 1 is selected from -SR, wherein R is selected from a sulfur protecting group, optionally substituted C 1-10 alkyl, optionally substituted aryl, optionally substituted acyl, and optionally substituted imidoyl; each instance of R 1, R 2, R 3, R 4, and R 5 is independently selected from hydrogen, halogen, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted heterocyclyl, optionally substituted aryl, -N 3, - NO 2, -N(R B) 2, -N(R A)C R A, -OR A, -OC R A, -SR A, -C N(R B) 2, -CN, -C R A, - C OR A, -S R A, -SO 2 R A, -SO 2 N(R B) 2, and -NHSO 2 R B; R 6 is -OH; L is selected from hydrogen, halogen, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted aryl, -N 3, -NO 2, -N(R B) 2, -N(R A)C R A, -OR A, -OC R A, -SR A, -C N(R B) 2, -CN, -C R A, - C OR A, -S R A, -SO 2 R A, -SO 2 N(R B) 2, -NHSO 2 R B, and substituted heterocyclyl; wherein: each instance of R A is independently selected from hydrogen, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted heterocyclyl, and optionally substituted aryl; and each instance of R B is independently selected from hydrogen, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted heterocyclyl, and optionally substituted aryl; and provided the glycan conjugate is not of the formulae (III-a) or (III-b): or (a) a glycan conjugate including a carrier and one or more glycans, and optionally (b) an adjuvant; X 1 is selected from -OR, wherein R is selected from an oxygen protecting group, optionally substituted C 1-10 alkyl, optionally substituted aryl, optionally substituted acyl, and optionally substituted imidoyl; or X 1 is selected from -SR, wherein R is selected from a sulfur protecting group, optionally substituted C 1-10 alkyl, optionally substituted aryl, optionally substituted acyl, and optionally substituted imidoyl; each instance of R 1, R 2, R 3, R 4, and R 5 is independently selected from hydrogen, halogen, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted heterocyclyl, optionally substituted aryl, -N 3, - NO 2, -N(R B) 2, -N(R A)C R A, -OR A, -OC R A, -SR A, -C N(R B) 2, -CN, -C R A, - C OR A, -S R A, -SO 2 R A, -SO 2 N(R B) 2, and -NHSO 2 R B; R 6 is -OH; L is selected from hydrogen, halogen, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted aryl, -N 3, -NO 2, -N(R B) 2, -N(R A)C R A, -OR A, -OC R A, -SR A, -C N(R B) 2, -CN, -C R A, - C OR A, -S R A, -SO 2 R A, -SO 2 N(R B) 2, -NHSO 2 R B, and substituted heterocyclyl; each instance of R A is independently selected from hydrogen, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted heterocyclyl, and optionally substituted aryl; and each instance of R B is independently selected from hydrogen, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted heterocyclyl, and optionally substituted aryl; and provided the glycan conjugate is not of the formulae (III-a) or (III-b): or