AQA · A-Level · Biology
Course version: 7402 · Version from Sept 2016
The use of vaccines to provide protection for individuals and populations…
Full specification wording
Cell recognition and the immune system: The use of vaccines to provide protection for individuals and populations against disease. The concept of herd immunity.
A vaccine introduces antigens into the body without causing the disease.
Checked against the AQA 7402 specification (opens in a new tab) on .
- Point 11 of 18
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
A vaccine introduces antigens into the body without causing the disease. Those antigens may come from a dead pathogen, an attenuated living pathogen, an isolated antigen, an inactivated toxin, or from mRNA that the body's own cells translate into the antigen. They trigger a primary response: clonal selection, division by mitosis and differentiation into plasma cells and, crucially, memory cells. If the real pathogen arrives later, memory B cells divide rapidly into plasma cells and produce a fast, large secondary response, so the person does not develop symptoms. Booster doses raise memory cell numbers further. Herd immunity operates on the population. If a large enough proportion of people are immune, an infected person is unlikely to meet a susceptible one, so transmission is interrupted and the pathogen cannot circulate.
What earns the marks
- The vaccine containing antigens, from a dead or attenuated pathogen or as an isolated antigen.
- A primary response producing memory cells without the person developing the disease.
- Memory cells producing a faster secondary response with a higher concentration of antibody on later exposure.
- Herd immunity described as a large enough proportion of the population being immune or vaccinated.
- Unvaccinated people being protected because the pathogen is less likely to be transmitted to them.
Common mistakes and how to put them right
Writing that a vaccine contains antibodies.
Put it right: It contains antigens and produces active immunity.
Saying vaccination makes a person immune immediately, when the primary response takes days.
Explaining herd immunity as unvaccinated people somehow catching immunity from vaccinated people.
Claiming everyone must be vaccinated, when herd immunity needs a sufficiently large proportion, not all.
Confusing attenuated, meaning weakened but alive, with dead.
Exam tips
- When asked how vaccination protects a population as well as an individual, write the two explanations separately; the population mark is for interrupted transmission.
- Name who benefits from herd immunity, for example babies too young to be vaccinated or immunocompromised patients, to earn the application mark.
- Use 'proportion' or 'percentage' of the population rather than 'lots of people'.
Try the lesson
The start of the Cell recognition and the immune system: The use of vaccines to provide protection for individuals and populations against disease. The concept of herd immunity. lesson, made from checked teaching notes for this specification point.
Have a go first
What is injected during vaccination to make a person immune to a disease?
Listen
A vaccine introduces antigens into the body without causing the disease. Those antigens may come from a dead pathogen, an attenuated living pathogen, an isolated antigen, an inactivated toxin, or from mRNA that the body's own cells translate into the antigen. They trigger a primary response: clonal selection, division by mitosis and differentiation into plasma cells and, crucially, memory cells. If the real pathogen arrives later, memory B cells divide rapidly into plasma cells and produce a fast, large secondary response, so the person does not develop symptoms. Booster doses raise memory cell numbers further. Herd immunity operates on the population. If a large enough proportion of people are immune, an infected person is unlikely to meet a susceptible one, so transmission is interrupted and the pathogen cannot circulate. A strong answer earns marks for these points. the vaccine containing antigens, from a dead or attenuated pathogen or as an isolated antigen. a primary response producing memory cells without the person developing the disease. memory cells producing a faster secondary response with a higher concentration of antibody on later exposure. herd immunity described as a large enough proportion of the population being immune or vaccinated. Exam tip: When asked how vaccination protects a population as well as an individual, write the two explanations separately; the population mark is for interrupted transmission.
See it
Key words
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antigens in vaccines
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memory cell formation
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secondary response
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herd immunity
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See every definition
- antigens in vaccines
- A vaccine introduces antigens into the body without causing the disease, and they may come from a dead pathogen, an attenuated living pathogen, an isolated antigen, an inactivated toxin, or from mRNA.
- memory cell formation
- The antigens trigger a primary response: clonal selection, division by mitosis and differentiation into plasma cells and, crucially, memory cells.
- secondary response
- On later exposure, memory B cells divide rapidly into plasma cells and produce a fast, large response, so the person does not develop symptoms.
- herd immunity
- If a large enough proportion of people are immune, an infected person is unlikely to meet a susceptible one, so transmission is interrupted and the pathogen cannot circulate.
Label the diagram
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1Box 1
2Box 2
3Box 3
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