The present invention provides methods for preparation of stable multivalent pneumococcal polysaccharide-protein conjugate vaccine formulations. Instant stable formulations show optimal percent adsorption for each conjugate wherein, aggregation can be prevented by employing i) Individual or separate adsorption for conjugates that otherwise show lower percent adsorption by combined adsorption ii) Histidine-Succinic acid buffer system along with shift in pH from neutral pH to acidic pH iii) a polysaccharide to protein ratio between 0.5 to about 1.4 iv) a six-bladed Rushton type turbine impeller in formulation vessels.
