Explain why a person who has recovered from a viral infection is often immune to that same virus in the future.

WJEC GCSE Biology (Wales) — 2.6.1 Pathogens and disease · Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

White blood cells produce antibodies that recognise the virus during the first infection.
Memory cells are created from these immune cells.
If the same virus re‑enters the body, memory cells recognise its antigen immediately.
They trigger a rapid, large‑scale antibody response that destroys the virus before symptoms appear.

Examiner tips

  • Use the exact terms ‘antibodies’, ‘memory cells’, and ‘antigen’.
  • Show the sequence: antibody production → memory cell formation → rapid response on re‑infection.
  • Mention that the response is faster and larger, preventing symptoms.

Common mistakes

  • Confusing antibodies with T‑cells only; forgetting to mention memory cells.
  • Saying the immune system ‘remembers’ without explaining how memory cells work.
  • Using vague terms like ‘immune response’ without specifying antibodies and memory cells.

Mark scheme (4 marks)

  1. White blood cells produce antibodies specific to the pathogen / antigen during the first infection
  2. Memory cells are produced during the first infection
  3. If the same pathogen enters the body again, memory cells recognise the antigen and respond faster / more quickly
  4. Antibodies are produced in large quantities / rapidly enough to destroy the pathogen before symptoms develop

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