Under polio prevention programme, infants in India were given polio vaccines on a large scale at regular intervals to eradicate polio from the country.
(a) What is a vaccine? Explain how does it impart immunity to the child against the disease.
(b) With the help of an example each, differentiate between active and passive immunity.
Solution
(a) A vaccine is a preparation containing a killed or attenuated pathogen or substances that mimic the disease-causing pathogen.
It imparts immunity to the child in following way:
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The inactivated pathogens in the vaccine, when introduced in the body, produce a primary immune response and antibodies are produced against the pathogen.
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Memory B and T cells are produced.
- Now, when the pathogen again attacks the person, memory B and T cells generate a massive immune response (secondary response) and the pathogen is killed
(b)
|
Active Immunity |
Passive immunity |
|
Body’s own cells produce antibodies in response to an infection. |
Antibodies from another person or animal are injected into the afflicted person. |
|
Person’s own immune response has to get activated and produce antibodies. Thus, it requires time for immunity development. |
Ready-made antibodies are injected into the afflicted person and, thus, immunity develops immediately. |
|
It is harmless. |
It may cause reactions. |
|
It provides long-lasting protection. |
Its effects are short-lived. |
| Example: Production of antibodies by the body against diseases such as chicken pox | Example: Injection of horse serum antibodies for treating diseases such as tetanus |
