(a) State the principle of immunisation. Name two diseases for which vaccine is available. (b) Mention two basic principles of prevention of infectious diseases

(a) Developing memory against a microbe, introduced deliberately to develop immunity against it.
For example : Polio, Typhoid.
(b) (i) Keeping cleanliness in everything be it personal and hygiene or public hygiene.
(ii) Availability of proper food and nourishment to keep immune system healthy.