Toxoids Cellular Fractions Combinations Passive Immunisation Immunoglobulins Anitisera Live Vaccines Live vaccines are prepared from live organisms. These organisms are passed through chick embryos or other such media repeatedly till they lose their capacity to induce the disease fully, but retain the capacity to trigger off the defence mechanism.
Live vaccines are usually more potent than inactivated vaccines.
They multiply within the host and produce more antigens. Usually one dose of live vaccine is enough for immunity. Some, as in the case of polio, need more. These should be spaced out. Effective storage is crucial for live vaccines.