How vaccines give immunity, herd immunity and coverage data, what antibiotics and painkillers do, and how resistant bacteria arise.
What you will learn
- Explain how a vaccine protects a person and a community
- Calculate vaccination percentages and compare them with a threshold
- Choose between antibiotics and painkillers
- Explain how antibiotic resistance develops and how to slow it
How a vaccine works
A vaccine holds a small amount of a dead or inactive pathogen.
Its antigens make lymphocytes produce the matching antibodies, and memory cells remain. If the real pathogen arrives, the right antibodies are made quickly and the person does not become ill.
When a large proportion of people is immune, the pathogen cannot spread: this herd immunity also protects babies and people who cannot be vaccinated.
- 4800 children, 4392 vaccinated, threshold 92%
- 4392 ÷ 4800 × 100 = 91.5%
- 91.5% is below 92%: herd immunity is not reached
To reach the target, 92% of 4800 is 0.92 × 4800 = 4416 children, so 4416 − 4392 = 24 more must be vaccinated. Cases do not fall to zero while some people are unvaccinated, because the pathogen can still spread among them.
The rest of this lesson and its 15 practice questions are locked.
In this lesson
- How a vaccine works
- Antibiotics and painkillers
- Antibiotic resistance
- Try it: Above or below the threshold
15 practice questions, marked as you go; about 25 minutes in all.
Key terms
Dead or inactive, Herd immunity, Antibiotics, Painkillers, Mutation, Strain
In this unit: Infection and response
Pathogens and how they spread, the body's defences and the immune system, vaccines, antibiotics and resistance, drug trials, and (Biology only) monoclonal antibodies and plant disease.