Question

The graph given below indicates the administration of the first (L) and second dose (M) of a vaccine. The corresponding response of the body is indicated by X, and Y. Interpret the graph and explain the reason for such a response shown by the body.

Answer 1

• On administration of the first dose of the vaccine (L), the body shows a response of low intensity (X) as the immune system comes in contact with the antigenic protein of the weakened/inactivated pathogen for the first time. This is called primary immune response.
• On subsequent encounters with the same antigenic protein in the second dose (M), the body elicits a highly intensified secondary response (Y). Because of the memory of the first contact with the antigen, the secondary immune response is faster and stronger, leading to more effective pathogen elimination in comparison to the primary immune response.