Which of the following does not increase the immunological effectiveness of DPT vaccine?

Hib polysaccharide is conjugated to a protein carrier like diphtheria toxoid (PRP-D) which increases its immunogenicity. But the immunogenicity of DPT vaccine is not increased by Hib vaccine. The peussis component in the DPT vaccine enhances the potency of the diphtheria toxoid. Adsorption of DPT vaccine on a mineral carrier like aluminium phosphate increases its immunogenicity. Ref: Park's Textbook Of Preventive And Social Medicine, By K. Park, 19th Edition, Page 137, 138; Ghai Essential Pediatrics, By O. P. Ghai, Piyush Gupta, V. K. Paul, 6th Edition, Page 196, 197.