The role of an active immune system is:

Raju of Class $IX$ was suffering from chickenpox. His friends Priya and Shaurya wanted to visit him. Shaurya's parents did not allow him to go. Priya had already suffered from it a few months before. Priya's parents allowed her to visit him. What could be the reason behind their parents' decision? What is the basis of the principle of immunisation?

$(a)$ What is immunisation?
$(b)$ Categorise the following into acute,chronic,infectious,or non-infectious diseases: Typhoid,$TB$,Goitre,Elephantiasis.

$(a)$ What are the two ways by which an infectious disease can be treated?
$(b)$ Explain the mode of action of antibiotics.

$(a)$ Who discovered the first vaccine?
$(b)$ Name two viral diseases that can be prevented by using vaccines. What is immunity?

During a health check-up camp in a school, the doctor talked about the prevention of diseases. Which six points will you share with your friend on the topic "prevention of diseases is more desirable than their successful treatment"?