Vaccination
Exam-ready definition
Giving a weakened or dead pathogen (or its antigens) to stimulate lymphocytes to produce antibodies and memory cells, so a later infection by the real pathogen triggers a faster, stronger immune response.
How this is marked
The mark schemes want 'memory cells' explicitly. That is the word that explains long-term immunity. Six-mark vaccination questions follow the chain: antigen → lymphocyte → antibodies → memory cells → faster secondary response.
In an exam answer
Explaining long-term protection: 'The vaccine triggers antibody production and memory cells, so on a second infection the antibodies are made faster and the pathogen is destroyed before symptoms appear.'
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