The following statements are true about DPT vaccine except :

Lets consider each choice one by one. Option ‘a’ : Two types of Diphtheria toxoid are in use now. ... Ananthnarayan 7/e, p 238 Fluid toxoid Adsorbed toxoid Adsorbed toxoid is purified toxoid adsorbed into insoluble aluminium compounds usually aluminium phosphate less often the hydroxide. Adsorbed toxoid is much more immunogenic than fluid toxoid. Option ‘b’ : Pertussis component in DPT (whole killed bacteria of bordetella pertusis) vaccine enhances the potency of the diptheria toxoid. Park 18/e, p 135 Most serous complication of DPT is neurological which is primarily due to pertusis component. Duration of immunity after whole cell pertusis vaccination is short lived, with little protection remaining after 10-12 years. Option ‘c’ : To reduce complications of whole killed bacteria of pertusis in DPT, acellular vaccine developed. Protection against pertussis by vaccines correlated best with the production of antibody to pertactin, fimbriae and pertussis toxin. All acellular pertussis vaccines currently available contain pertussis toxoid. Acellular vaccine is more immunogenic has less adverse effects. It is given as DTaP. CMDT ‘06, p 1304 Option ‘d’ : Quadriple vaccine of DPT with H.influenza B is available in India but conjugate vaccine (eg. HIb vaccine) do not interfere with immunogenicity of simultaneously given other vaccines.