The present invention relates to novel polysaccharide-protein conjugates and process to obtain the same. More particularly, the present invention relates to polysaccharide-protein conjugates produced using carbamate chemistry capable of being used in production of monovalent vaccine or multivalent combination vaccines as well as a diagnostic tool. More specifically the present invention relates to Neisseria meningitidis serogroup X, A, C, Y and W135 polysaccharide–carrier protein conjugate using carbamate chemistry and the process to obtain the same.