What is the basic principle of vaccination ? How do vaccines prevent microbial infections ? Name the organism from which hepatitis B Vaccine is produced.

Explanation

The principle of vaccination is based on the property of .memory. of the immune system .
In vaccination, a preparation of antigenic proteins of pathogens or inactivated/live but weakened pathogens is introduced into the body.
The antigens generate the primary immune response by producing antibodies. The vaccines also generate the memory B-cells and T-cells.
When the vaccinated person is attacked by the same pathogens, the existing memory B-cells or T-cells recognise the antigen quickly and overwhelm the invaders with massive production of lymphocytes and antibodies.
Hepatitis B vaccine is produced from yeast.