Explain how vaccination protects a person from becoming seriously ill when they are later infected by a pathogen.

WJEC GCSE Biology (Wales) — 2.8 Disease, defence and treatment · Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

A vaccine contains antigens from the pathogen, or a weakened or dead form of the pathogen that carries antigens. These antigens are recognised by white blood cells (lymphocytes), which produce specific antibodies. The immune response also creates memory cells that remain in the body. If the person is later infected, the memory cells recognise the pathogen immediately and trigger a rapid, large antibody response, destroying the pathogen before it can cause serious illness.

Examiner tips

  • Use the exact terms – antigens, lymphocytes, antibodies, memory cells
  • Show the sequence: vaccine → antibody production → memory cells → rapid response on re‑exposure
  • Mention that the response is faster and larger, preventing serious disease

Common mistakes

  • Confusing the vaccine with the pathogen itself; not mentioning antigens
  • Failing to state that memory cells enable a quicker response
  • Using vague language such as "immune system" instead of specific cells and antibodies

Mark scheme (4 marks)

  1. The vaccine contains antigens (from the pathogen) / weakened or dead pathogens that carry antigens
  2. White blood cells (lymphocytes) produce antibodies in response to the antigens
  3. Memory cells are produced / remain in the body after the initial immune response
  4. On re-exposure to the pathogen, memory cells allow a faster / larger antibody response so the pathogen is destroyed before the person becomes seriously ill

Key terms in this question

vaccination

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