Why do we fall ill: Questions and Answers Chapter 13 For Class 9th (CBSE/NCERT)

Ans: It is a process that develops our body’s resistance to disease-causing germs. In this procedure, a healthy person receives an injection of a vaccine to help them build immunity to a particular disease. Our immune system, therefore, engages in combat with a dead or attenuated microorganism in the form of vaccination to strengthen immunity against the same disease. When the bacterium returns, the immune system’s cells are aware of it and rapidly dispatch it.