Vaccination

1. 1 State [1 mark]

   State what a vaccine contains.

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   Model answer

   Small quantities of dead or inactive forms of a pathogen.

   Mark scheme

   • Dead or inactive pathogens — 1 mark
2. 2 Explain [3 marks]

   Explain how a vaccination against measles prevents a child from catching measles.

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   Model answer

   The vaccine contains a dead or inactive form of the virus. This stimulates the white blood cells to produce antibodies. If the real virus enters the body later, the white blood cells quickly produce the correct antibodies, so the virus is destroyed before it makes the child ill.

   Mark scheme

   • Dead or inactive virus stimulates antibody production — 1 mark
   • Quick response on re-infection — 1 mark
   • Virus destroyed before illness — 1 mark
3. 3 Explain [2 marks]

   Explain why vaccinating most of the population protects people who have not been vaccinated.

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   Model answer

   The pathogen cannot spread easily, because most of the people it meets are immune. This means unvaccinated people are less likely to come into contact with it.

   Mark scheme

   • Most people immune so the pathogen cannot spread — 1 mark
   • Fewer chances for unvaccinated people to be infected — 1 mark
4. 4 Explain [2 marks]

   Explain why a person who has been vaccinated against a disease does not become ill if they are later infected by the same pathogen.

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   Model answer

   Memory cells respond quickly and make the correct antibodies. The pathogen is destroyed before it can cause the disease.

   Mark scheme

   • Fast production of the correct antibodies — 1 mark
   • Pathogen destroyed before illness — 1 mark
5. 5 Suggest [3 marks]

   The percentage of children vaccinated against measles in one town fell from 95% to 80%. Suggest what might happen to the number of measles cases and explain why.

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   Model answer

   The number of measles cases is likely to rise. With fewer children immune, the virus can spread more easily from person to person. There is no longer enough herd immunity to protect those who are not vaccinated.

   Mark scheme

   • Cases are likely to increase — 1 mark
   • Fewer immune people so easier spread — 1 mark
   • Loss of herd immunity — 1 mark
6. 6 Evaluate [4 marks]

   Evaluate the use of vaccination to control the spread of disease around the world.

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   Model answer

   Vaccination has saved millions of lives and has wiped out smallpox. It is cheaper than treating a disease, and it protects people who cannot be vaccinated. However, some viruses, such as flu, change, so new vaccines are needed. A small number of people have a reaction to a vaccine, and fear of this can reduce the number vaccinated. Overall the benefits outweigh the risks.

   Mark scheme

   • Saves lives / eradication — 1 mark
   • Cheaper than treatment — 1 mark
   • Some pathogens change / limits — 1 mark
   • A reasoned conclusion — 1 mark
7. 7 Describe [4 marks]

   Describe how a vaccine causes the immune system to be ready for a later infection.

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   Model answer

   The vaccine contains a dead or inactive form of the pathogen, with its antigens. The white blood cells recognise the antigens and make antibodies. Some of them remain as memory cells. When the real pathogen enters later, the correct antibodies are made very quickly.

   Mark scheme

   • Dead or inactive pathogen with antigens — 1 mark
   • Antibodies are made — 1 mark
   • Memory cells remain — 1 mark
   • Fast response to the real pathogen — 1 mark

Quick check

1. 1

   What does a vaccine contain?

   1. ALive pathogens that cause disease
   2. BDead or inactive pathogens
   3. CAntibiotics
   4. DPainkillers
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   B: Dead or inactive pathogens

   A vaccine contains dead or inactive pathogens, so it cannot cause the disease.

2. 2

   What does a vaccine stimulate the white blood cells to do?

   1. AMake toxins
   2. BEngulf platelets
   3. CProduce antibodies
   4. DClot the blood
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   C: Produce antibodies

   Vaccines stimulate the production of antibodies.

3. 3

   Why is a second infection dealt with more quickly after vaccination?

   1. AMemory cells respond quickly
   2. BThe pathogen is weaker
   3. CThe skin is thicker
   4. DRed blood cells attack it
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   A: Memory cells respond quickly

   Memory cells quickly make the correct antibodies.

4. 4

   What is herd immunity?

   1. AImmunity in farm animals only
   2. BImmunity for one person
   3. CImmunity to every disease
   4. DProtection of a population when most are immune
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   D: Protection of a population when most are immune

   When most people are immune, the disease cannot spread, and the unvaccinated are protected.

5. 5

   Which disease has been eradicated by vaccination?

   1. AMeasles
   2. BSmallpox
   3. CMalaria
   4. DGonorrhoea
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   B: Smallpox

   Smallpox has been wiped out by a world-wide vaccination programme.

6. 6

   What happens to the spread of a disease if fewer people are vaccinated?

   1. AIt increases
   2. BIt decreases
   3. CIt stops
   4. DIt stays the same
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   A: It increases

   There are more people who can catch and pass on the disease, so it spreads more.

7. 7

   Why can flu vaccines need updating?

   1. AFlu is caused by bacteria
   2. BFlu has no antigens
   3. CThe virus changes
   4. DAntibodies are not specific
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   C: The virus changes

   The antigens on flu viruses change, so old vaccines no longer work.

8. 8

   Why are babies who cannot be vaccinated still protected when most other people are vaccinated?

   1. AThey make their own antibiotics
   2. BTheir skin is thicker
   3. CThey have more white blood cells
   4. DThe pathogen is unlikely to reach them
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   D: The pathogen is unlikely to reach them

   The pathogen cannot spread easily when most people are immune, so the babies are unlikely to meet it.