The present invention relates to an improved process of conjugation to obtain synthetic oligosaccharide - protein (OS-PR) conjugates. The process of synthetic OS-PR conjugation is a rapid process providing oligosaccharide - protein conjugates which are highly irnrnunogenic and elicit specific and hornogenous immune responses. The synthetic oligosaccharide cornprising of four to eight repeating units of respective rnonorners and at least one in-built terminal arnino linker, said synthetic polysaccharide rnimics natural polysaccharide obtained from gram negative bacteria such as Neisseria meningitidis serogroups A, C, Y, W, X and Haemophilus influenzae and carrier protein is obtained from gram positive bacteria such as Clostridiurn tetani ( tetanus toxoid) or Corynebacterium diphtheriae (CRM197) or their recombinant versions. The conjugation chemistry of the said oligosaccharide-protein conjugate of the present invention is thio-ether linkage. The present invention takes complete process tirne in the range of 14-22 hours.The said oligosaccharide-protein conjugates are useful in production of monovalent vaccine or multivalent combination vaccines and as diagnostic tool.
