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CBSE 2023 · Region 1 · Set 1 · Q32 · 5 marks

A time-bound vaccination programme is followed for the children in our country from their birth up to ten years of age. A graph plotted below shows the effect of the vaccination followed by infection by the same pathogen, and the antibody concentration in the blood of the child.
Figure: CBSE Class 12 Biology 2023, Human Health and Disease
(i)
Explain why the administration of a vaccine causes an increase in the antibody concentration.
(ii)
If the child is infected with the same pathogen almost four months later, the antibody concentration in his/her blood increases very fast. Explain why.
(iii)
A table given below gives information about different types of immunity and how they are attained. Identify 'P', 'Q', 'R', 'S' and ' T ' in the table.
Type of immunityProduction of antibodiesPresence of memory cellsMode attained
($\displaystyle 1$)Natural, activeYes'P''Q'
($\displaystyle 2$)Natural, passiveNo'R'Across the placenta during pregnancy/breast feeding
($\displaystyle 3$)Acquired, active'S'YesGetting a vaccine during breast feeding
($\displaystyle 4$)Acquired, passive'T'NoGetting an injection of antibodies

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