VMC 221: Veterinary Immunology and Serology (1+1)

Inactivated or Killed vaccines

INACTIVATED/KILLED VACCINE

• Inactivated vaccine is prepared by physical or chemical treatment to the pathogen so that the organisms become inactive (loses replication capability) but maintains its immunogenicity.
• The procedure should not disturb the immunogenic structures or epitopes, but should remove the replication or virulence of the organisms. This vaccine is usually prepared with a virulent strain and the vaccine is more immunogenic.
• In general these kinds of vaccine are used when attenuated vaccines are not available or for an outbreak where characterization of the organism is not determined and pathogenicity have not been assessed.
• Examples of chemical inactivating agents are formaldehyde, glutaraldehyde, beta propiolactone etc., they change the structural conformation or cross link the structures and ultimately inactivate the organisms.
• The physical inactivating agents are gamma irradiation, U-V irradiation etc. which are going to change the structural conformation or cross – linking structures.
• In general, inactivated vaccine requires an adjuvant to increase the potency of the vaccine.
• Advantages
  • No possibility of reversion
  • No shedding and contamination of environment
  • Quite stable, thus less need for cold chain
  • More immunogenic 
  • Whole organism has both T and B epitopes.
• Disadvantages
  • Cannot replicate so antigen is limited
  • Require, multiple doses, adjuvants and boosters vaccination
  • If not properly inactivated, it may cause disease outbreaks
  • Increased risk of allergic reactions due to large amounts of antigen involved
  • Costly
  • May be ineffective against intracellular organisms.