Fish Immunology (1+1)

Unit 14 - Vaccine

14.3. Live-attenuated vaccines
Live-attenuated vaccine is a suspension of attenuated live pathogens that are able to replicate inside the host and induce protective immune response but unable to cause disease. To make an attenuated vaccine, the pathogen is grown in foreign host such as animals, embryonated eggs or in tissue culture under controled conditions and altered to a non-pathogenic form to make it less virulent. They mimic the actual infection by pathogens and hence a small dose of vaccine is enough to induce long lasting protective immune response. Live attenuated vaccines can induce both humoral and cell-mediated immune responses.
Advantages

• Live-attenuated vaccine can stimulate cellular immune responses, memory cells as well as humoral immune responses.
• Administrating lesser quantities is sufficient to induce protection.
• Single administrating of vaccine is sufficient to produce high efficacy and long lived immunity.
• Administration of live attenuated vaccine has a possibility to stimulate immune response to all protective antigens.

Disadvantages

• Live-attenuated vaccine may rarely revert to its virulence form and cause disease.
• Live-attenuated vaccine cannot be given to immunosuppressed individuals.
• Since they are live they require proper storage.