The present invention relates to polysaccharide – protein conjugates with enhanced immunogenicity displaying significantly high antibody titres. The carrier protein is obtained from group of gram positive bacteria, polysaccharide fragment is obtained from group of gram negative bacteria, preferably from Haemophilus influenzae serotype b (Hib), Neisseria meningitidis serogroup A and C (MenA and MenC). The present invention also relates to a rapid and high yielding process of preparing the polysaccharide–protein conjugates in which derivatized carrier protein reacts with cleaved and depolymerized polysaccharide fragments of optimum length to obtain polysaccharide – protein conjugate employing reductive amination chemistry. The present invention further relates to a chemical process of polysaccharide fragmentation to optimum length for use in conjugation.
