Fiducia TogetherInfection and immunity
Pathogens, how the body fights them, and how vaccines work.
Please note: This page explains a word or a process in education. It is general information about the system, the law and the guidance in England — not advice about your child, your school or your exam. If a decision is going against you, get advice from one of the free services we link to before you agree to anything or miss a deadline. If you are revising, check your own exam board's specification: boards word things differently and yours is the one that marks you.
What it is
Pathogens are disease-causing microorganisms: bacteria, viruses, fungi and protists. Defences include barriers (skin, mucus, stomach acid) and the immune response — white blood cells engulfing pathogens, producing antibodies and producing antitoxins.
Where it applies
GCSE biology and combined science.
How it works
A vaccine introduces dead or inactive pathogen, so the body produces antibodies and memory cells without the disease. On re-exposure the response is faster and larger, so the person does not become ill.
Herd immunity means enough of a population is immune that the pathogen cannot spread easily, protecting those who cannot be vaccinated.
How to use it in your work
For vaccination, the answer is always: dead or inactive pathogen, antibodies produced, memory cells remain, faster and larger response on re-infection. Four marks, four clauses.
Antibiotics kill bacteria and do not affect viruses. Say why: viruses reproduce inside cells.
Antibiotic resistance is natural selection — use that vocabulary.
Where to get help
Your teacher, your board's specification for the depth required at your tier, and Bitesize for the diagrams.
Revise this with a song
These are ours. We write revision songs because a lot of people remember a tune when they cannot remember a page, and because revising out loud in the kitchen beats staring at a highlighter.
- The Biology Song The GCSE biology specification, set to music.
Where to read more
Last reviewed 2026-08-28 by Fiducia Together · Next review due 2027-08-28
Please note: This page explains a word or a process in education. It is general information about the system, the law and the guidance in England — not advice about your child, your school or your exam. If a decision is going against you, get advice from one of the free services we link to before you agree to anything or miss a deadline. If you are revising, check your own exam board's specification: boards word things differently and yours is the one that marks you.