Vaccination protects people against many diseases. A vaccine holds a weak or dead form of a pathogen. It may also hold parts of the pathogen. These cannot c...
Question 1 Report
Vaccination protects people against many diseases. A vaccine holds a weak or dead form of a pathogen. It may also hold parts of the pathogen. These cannot cause the disease. The vaccine goes into the body. The immune system acts as if the real pathogen is there. But the person does not get ill. A health worker spoke to some parents. She said vaccines protect their children. She said they also protect others who cannot be vaccinated. Some parents did not see how this could work. A student was asked to explain the science. The questions below are about how vaccines protect people.
(a) State what a vaccine usually contains. [1]
(b) Explain how a vaccine causes a person to become immune to a disease. [4]
(c) Name the type of immunity produced by a vaccine. [1]
(d) Explain how vaccinating most of a community helps to protect the few people who cannot be vaccinated. [3]
(e) Suggest one reason why some people in a community cannot be vaccinated. [1]
Answer Details
(a) A vaccine usually contains a weakened or dead form of the pathogen, or its antigens [1].
(b) A vaccine makes a person immune as follows: the antigens in the vaccine are recognised by lymphocytes (white blood cells) [1]; the lymphocytes make antibodies specific to those antigens [1]; and memory cells are produced [1]; so if the real pathogen enters later, the memory cells make antibodies very quickly and in large amounts, destroying it before the person becomes ill [1].
(c) This is active immunity [1], because the body makes its own antibodies.
(d) Vaccinating most of a community protects the few who cannot be vaccinated because vaccinated people do not catch or spread the disease [1], so there are far fewer people able to pass the pathogen on [1], making it very unlikely that an unvaccinated person ever meets the pathogen (this is herd immunity) [1].
(e) One reason a person cannot be vaccinated (any one): they are too young, they are already ill or have a weakened immune system, or they are allergic to the vaccine [1].
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