Table 1.

Advantages and disadvantages of live (attenuated) virus and killed (inactivated) virus vaccines

	Advantages	Disadvantages
Live vaccines	Mode of action is most similar to natural infection Multiply in host; induce range of immune responses Duration of immunity is usually long lasting No adverse side effects to foreign protein	Possible reversion to virulence Possible contaminating viruses Inference by other agents and passive antibody Storage problems (heating) Possible production of latency Possible induction of abortion Possible shedding to susceptible cohort Temporary immune suppression up to 2 weeks
Killed vaccines	Quite stable Easy to produce	Require large amounts of antigen or may not contain protective antigens Reactions can develop to foreign proteins or adjuvants Immunity is usually short-lived; multiple boosters are required Do not produce local immunity May not inactivate all the agent Other agents that are resistant to inactivating agent may be present (eg, prions) May induce aberrant disease

Adapted from Tizard IR. The use of vaccines. In: Tizard IR, editor. Veterinary immunology: an introduction. 8th edition. Philadelphia: Saunders; 2008; with permission.