how does vaccines help even thoughthey are dead or weak organisms??????????

Dear Student,

Vaccination may be defined as protection of the body from communicable diseases by the administration of some agents that mimic the microbe. The agent can be a suspension of killed or attenuated microbes, or a substance that mimics the disease-causing microbes. This is known as a vaccine. Vaccination is based on specific ways of defence provided by the immune system of a person. For example, we know that if a child has suffered from small pox once, then there is almost no chance of him suffering from it again. This happens because when the immune system of the body encounters a virus for the first time, it reacts against it and remembers it.  Therefore, when small pox virus attacks the body for a second time, the immune system reacts strongly to prevent chances of suffering from the disease again. Therefore, it can be concluded that if we infect the body of a person with something that mimics the microbe, then the immune system will remember it, and prevent the actual disease-causing microbe from causing any disease. It forms the basis of vaccination.

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