Describe how vaccination protects a person from disease. Include the role of white blood cells in your answer.

AQA A-Level Biology (7402) — 3.2.4 Cell Recognition and the Immune System · Describe · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (5 marks)

The vaccine contains antigens from a pathogen (or a dead/ weakened form of it). These antigens are recognised by white blood cells – mainly lymphocytes – which produce specific antibodies. During this primary response memory cells are created. If the same pathogen later enters the body, the memory cells recognise its antigen instantly and trigger a rapid secondary immune response. A large amount of antibody is then produced quickly enough to destroy the pathogen or prevent it from causing symptoms, so the person does not become ill.

Examiner tips

  • Use the word ‘antigens’ and ‘antibodies’ – examiners look for these terms.
  • Show the sequence: vaccine → lymphocyte → antibody + memory cells → rapid response on re‑exposure.
  • Mention that memory cells are key to the speed and strength of the second response.
  • Keep the answer concise – 5 marks, so one sentence per point is sufficient.

Common mistakes

  • Confusing antigens with antibodies; they are different. Failing to mention memory cells or the rapid secondary response. Using vague language such as ‘immune system’ without specifying lymphocytes or antibodies.

Mark scheme (5 marks)

  1. The vaccine contains antigens (from a pathogen / dead or weakened pathogen)
  2. White blood cells (lymphocytes) produce antibodies in response to the antigen
  3. Memory cells are produced during this initial immune response
  4. If the same pathogen enters the body again, memory cells recognise the antigen and respond more quickly
  5. Antibodies are produced in large quantities rapidly enough to prevent the person becoming ill / destroying the pathogen before symptoms develop

Key terms in this question

vaccination

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