One alternative to using live organisms in vaccine development is killing or inactivating the microbe. Killed inactivated vaccines are very efficacious like the live attenuated vaccines. The causative agent or microbe used for the development of killed inactivated vaccines is usually inactivated by physical and chemical treatments. Vaccines of this type are generally created by inactivating a pathogen, typically using heat or chemicals such as formaldehyde or formalin as aforementioned; and such chemical and physical treatment makes the organism used to be non-pathogenic. This destroys the pathogen’s ability to replicate in a human host. Examples of killed inactivated vaccines include: Inactivated Polio Vaccine (IPV), oral cholera vaccine, rabies vaccine and seasonal influenza vaccine. Toxoids vaccines are also prepared from inactivated toxic compounds of microbes. Some bacterial diseases are not caused by the bacterium itself, but by the toxins that they produce. Examples of such infections include tetanus caused by the neurotoxins produced by Clostridium tetani.
MERITS OF KILLED INACTIVATED VACCINES
- Killed inactivated vaccines are safe to use since they cannot revert to a more virulent form capable of causing disease in the individual. They can be administered to immunodeficient persons and pregnant women.
- They are cheaper than live attenuated vaccines.
DEMERITS OF KILLED INACTIVATED VACCINES
- They provide a short length of protection than the live vaccine.
- Periodic booster doses are required to maintain long term immunity.
- Inactivation, such as by formaldehyde in the case of Salk vaccine, may alter the antigenicity of the vaccine virus. And this might lead to delayed activation of the host’s immune system.
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