What are the four types of pathogen?

The four types of pathogen are bacteria, viruses, fungi and protists. Bacteria can release toxins that damage cells, viruses reproduce inside cells and burst them, fungi such as rose black spot affect plants and skin, and protists such as the malaria parasite are often spread by vectors like mosquitoes.

How does the immune system fight a pathogen?

White blood cells defend the body. Phagocytes engulf and digest pathogens, and lymphocytes produce antibodies with a shape specific to the pathogen's antigens, marking them for destruction and clumping them together. Lymphocytes also make antitoxins that neutralise toxins. After infection, memory cells give long-term immunity.

How does a vaccine work?

A vaccine contains a dead or inactive pathogen, or its antigens. This makes lymphocytes produce antibodies and memory cells without the person becoming ill. If the real pathogen later enters, the memory cells produce the correct antibodies faster and in larger amounts, destroying it before it causes disease.

How are new drugs tested?

New drugs are first tested in preclinical trials on cells and tissues, then on animals, to check for toxicity, efficacy and dose. They then go through clinical trials on healthy volunteers (for safety) and on patients (for dose and efficacy), often using a placebo and a double-blind design to remove bias, before approval.

EnglandCombined Science

Edexcel GCSE Combined Science CB5 Health, disease and medicines: a complete overview of pathogens, immunity, non-communicable disease and drug development

Q: What does Edexcel Combined Science CB5 cover?

CB5 covers communicable diseases and the four types of pathogen, how pathogens spread and are controlled, the body's physical and chemical defences, the immune response and antibodies, vaccination, non-communicable diseases and their risk factors, and the development and testing of new drugs through preclinical and clinical trials.

A deep-dive Edexcel GCSE Combined Science guide to Topic 5 (CB5) Health, disease and the development of medicines. Covers communicable diseases and the four pathogens, how pathogens spread, the body's defences, the immune response and antibodies, vaccination, non-communicable diseases and risk factors, and how new drugs are developed and tested.

Generated by Claude Opus 4.813 min readCB5Updated 2026-06-02

Reviewed by: AI editorial process; not yet individually human-reviewed

Jump to a section

What CB5 actually demands
Communicable disease and immunity
Non-communicable disease
Developing medicines
How CB5 is examined
Check your knowledge

What CB5 actually demands

Health, disease and the development of medicines is a heavily examined topic that splits into infectious disease (pathogens and the immune system) and non-infectious disease (risk factors and drug development). The examiners reward precise use of the words antigen, antibody, phagocyte and lymphocyte, and a clear understanding of correlation versus cause.

This guide walks through the two halves of the topic and ties together the matching dot-point pages, each with its own practice questions.

Communicable disease and immunity

A pathogen is a disease-causing microorganism: bacteria, viruses, fungi or protists. They spread by air, water, direct contact and vectors. The body's first line of defence is non-specific: the skin, mucus and cilia, and stomach acid.

If a pathogen gets in, white blood cells respond. Phagocytes engulf pathogens; lymphocytes make antibodies specific to the pathogen's antigens, and antitoxins. Memory cells give immunity. A vaccine uses a dead or inactive pathogen to trigger this response safely, so a later infection is destroyed quickly.

Non-communicable disease

A non-communicable disease cannot spread between people; examples are heart disease, type 2 diabetes and many cancers. Risk factors (smoking, poor diet, lack of exercise, alcohol) increase the probability of disease. A correlation is not proof of cause: a mechanism and controlled studies are needed.

Developing medicines

New drugs are tested in stages. Preclinical trials use cells, tissues and animals to check toxicity, effect and dose. Clinical trials use healthy volunteers then patients, often with a placebo and a double-blind design to remove bias, before peer review and approval.

How CB5 is examined

Process recall. Describing the immune response and how vaccines work.
Vocabulary. Distinguishing antigen, antibody, phagocyte and lymphocyte.
Data interpretation. Reading antibody-response graphs and judging correlations.
Sequencing. Putting the stages of drug development in the right order.

Check your knowledge

A mix of recall and application questions covering CB5. Attempt them under timed conditions, then check against the solutions.

Name the four types of pathogen. (2 marks)
State two ways pathogens can spread. (2 marks)
State the role of a phagocyte. (1 mark)
State the role of an antibody. (1 mark)
Explain how a vaccine gives immunity. (3 marks)
Define a non-communicable disease. (1 mark)
Define a risk factor. (1 mark)
State what is tested in preclinical trials. (1 mark)

Sources & how we know this

Edexcel GCSE (9-1) Combined Science (1SC0) specification — Pearson (2016)