How do vaccines give immunity, and what do antibiotics treat?
How vaccination produces immunity, how antibiotics treat bacterial infections, and the problem of antibiotic resistance.
A focused answer to the WJEC GCSE Science Double Award Unit 4 topic on vaccines and antibiotics, covering how vaccination produces immunity, how antibiotics treat bacterial infections but not viruses, and the problem of antibiotic resistance.
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What this dot point is asking
WJEC Double Award Unit 4 wants you to explain how vaccination produces immunity, how antibiotics treat bacterial infections, and the problem of antibiotic resistance.
How vaccines work
This gives immunity without the person having to catch the disease. If most of a population is vaccinated, the disease cannot spread easily, which protects others too (herd immunity).
How antibiotics work
Because antibiotics only affect bacteria, they cannot treat viral diseases such as the common cold or flu. Using the right antibiotic clears a bacterial infection by killing the bacteria inside the body, without harming the patient's own cells.
Antibiotic resistance
To slow resistance, antibiotics should only be used when needed, and patients should finish the whole course.
Why finishing the course matters
Doctors tell patients to finish the whole course of antibiotics, even when they feel better. This is because stopping early may leave some of the more resistant bacteria alive; these can then multiply and spread, making the infection harder to treat and helping resistance to develop. Finishing the course makes sure all the bacteria are killed. This, along with not using antibiotics for viral infections, is a key way of slowing antibiotic resistance, and is a common exam point.
How new medicines are tested
New medicines, including antibiotics, must be tested before they can be used, and exam questions sometimes ask about this. They are first tested for toxicity (safety) and to see if they work, often on cells and then animals, and finally in clinical trials on healthy volunteers and then patients. The trials check the medicine is safe, finds the right dose, and confirms it actually works. This careful testing protects patients but means developing a new medicine takes many years and is expensive, which is one reason antibiotic resistance is such a concern.
Herd immunity
When a large enough proportion of a population is vaccinated, even people who are not vaccinated are protected, because the disease cannot spread easily from person to person. This is called herd immunity. It matters because some people (such as very young babies or those who are ill) cannot be vaccinated, and herd immunity helps protect them. If too few people are vaccinated, outbreaks can return. Being able to explain how vaccinating most of a population protects everyone is a common higher-mark point.
Try this
Q1. What does a vaccine contain? [1 mark]
- Cue. A dead or weakened (inactive) form of the pathogen.
Q2. Why do antibiotics not work on the flu? [1 mark]
- Cue. Flu is caused by a virus, and antibiotics only kill bacteria.
Exam-style practice questions
Practice questions written in the style of WJEC exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
WJEC style5 marksExplain how a vaccine makes a person immune to a disease.Show worked answer →
A Unit 4 extended question worth 5 marks. Reward: a vaccine contains a dead or weakened (inactive) form of the pathogen (or its antigens) (1); this is harmless but the body's white blood cells still respond (1) by producing antibodies against it (1); the body also makes memory cells that stay in the body (1); so if the real pathogen later invades, the memory cells produce antibodies quickly and in large amounts, destroying it before the person becomes ill (1). Markers credit the dead/weakened pathogen, antibody production, memory cells, and the fast response on reinfection. A common error is to say the vaccine kills the pathogen directly.
WJEC style3 marksExplain why antibiotics cannot be used to treat the common cold, and why overusing antibiotics is a problem.Show worked answer →
A Unit 4 explain question. Reward: the common cold is caused by a virus, and antibiotics only kill bacteria, not viruses (1); overusing antibiotics leads to antibiotic resistance, as resistant bacteria survive and reproduce by natural selection (1); resistant bacteria are then hard to treat, so antibiotics should only be used when needed (1). Markers credit antibiotics not working on viruses, and overuse causing resistance. A common error is to say antibiotics kill viruses.
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