GCSE · Biology · AQA · Spec 8461

Vaccination

You can become immune to a disease without ever catching it. And when enough people around you are vaccinated, that helps protect someone who can't or won't be vaccinated.

One person, two meetings with the same pathogen

Stages 1 and 2 are the vaccination. Stages 3 to 5 happen later, when the same pathogen gets in. Open any stage to see why it matters.

Zoom out to a whole population

Reason it through

How can other people's vaccinations protect someone who is unable to be vaccinated?

Link 1 of 4

First link · your turn

Start with the population. How many people in it are vaccinated?

Locked — reveal the link above first

What do you think?

Who does it protect?

In one town, most people have been vaccinated against a pathogen. A few people in the town can't or won't be vaccinated.

Who does vaccinating a high proportion of this town protect? Pick the idea closest to what you think right now.

Only the people who had the vaccine. A vaccine works inside your own body, so it can only protect you.Everyone, but only once every single person in the town has been vaccinated.Everyone, even if only a few people in the town had been vaccinated.The vaccinated people, and also the people who can't or won't be vaccinated.

How sure are you?

I'm sureI think soI'm guessing

Only the people who had the vaccine. A vaccine works inside your own body, so it can only protect you.

This is a common misconception

The first half is right: the vaccine works through your own white blood cells. But being immune also means you are less likely to pass the pathogen on. When most people are vaccinated, the pathogen spreads less far and is less likely to reach the people who can't or won't be vaccinated, so they gain protection too. That is the chain you have just built.

Everyone, but only once every single person in the town has been vaccinated.

This is a common misconception

Herd immunity does not need every single person. It needs a high proportion of the population to be vaccinated. That is why the few people who can't or won't be vaccinated can still be protected: they are the ones it protects.

Everyone, even if only a few people in the town had been vaccinated.

This is a common misconception

A few is not enough. With no vaccination, or vaccination of only a few people, a pathogen can keep passing easily between people, so it can still reach the unvaccinated. It is necessary to vaccinate a high proportion of a population to provide herd immunity.

The vaccinated people, and also the people who can't or won't be vaccinated.

This matches the evidence

Yes. Vaccination can make the vaccinated people immune, and because most people are vaccinated the pathogen is less likely to reach anyone who is not. Herd immunity helps protect those who can't or won't have the vaccination, and it depends on a high proportion of the population being vaccinated.

A high proportion vaccinated protects the vaccinated and helps protect the unvaccinated. A few vaccinated is not enough.

Your turn to write it

Explain it in your own words

Explain how vaccination prevents illness in an individual, and how vaccinating a large proportion of a population reduces the spread of a pathogen. [6 marks]

Your answer

0 words · your answer stays on this page and is not sent anywhere.

The mark scheme

Small quantities of a dead or inactive form of the pathogen are introduced into the body. (1 mark)
This stimulates the white blood cells to produce antibodies. (1 mark)
If the same pathogen re-enters the body, the white blood cells respond quickly. (1 mark)
They produce the correct antibodies, which prevents infection. (1 mark)
When most people are vaccinated, the pathogen cannot pass easily between people, so it spreads less far. (1 mark)
So it is less likely to reach people who are unable to be vaccinated, who are protected too (herd immunity). (1 mark)

Model answer

A vaccine puts small quantities of a dead or inactive form of the pathogen into the body. This stimulates the white blood cells to produce antibodies. If the same pathogen gets into the body later, the white blood cells respond quickly and produce the correct antibodies, so infection is prevented and the person does not become ill. If a large proportion of the population is vaccinated, fewer people can pass the pathogen on, so it cannot spread easily between people. This means it is less likely to reach people who are unable to be vaccinated, so they are protected as well. This is herd immunity.

Order is the whole answer: introduce, stimulate, re-enter, respond quickly with the correct antibodies, then zoom out to the population.

Exam line: Give the individual sequence in order, then the population: most vaccinated, so it spreads less far, so it is less likely to reach those who can't be vaccinated.

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

What you need to know

A vaccine introduces small quantities of a dead or inactive form of a pathogen into the body.
This stimulates the white blood cells to produce antibodies.
If the same pathogen re-enters the body, the white blood cells respond quickly to produce the correct antibodies, preventing infection.
Vaccination can make a person immune to a pathogen without them first having to catch the disease.
Vaccinating a high proportion of a population reduces the spread of a pathogen and helps protect those who can't or won't be vaccinated (herd immunity).

The big picture

Vaccination introduces small quantities of a dead or inactive form of a pathogen, which stimulates the white blood cells to produce antibodies. If the same pathogen later re-enters the body, the white blood cells respond quickly to produce the correct antibodies, preventing infection, so the person is immune without first having to catch the disease. When a high proportion of a population is vaccinated, the pathogen spreads less far and is less likely to reach people who can't or won't be vaccinated: this is herd immunity.

Key points

1Vaccine: small quantities of a dead or inactive pathogen, which stimulate white blood cells to produce antibodies.

2Same pathogen later: white blood cells respond quickly with the correct antibodies, so infection is prevented.

3Immunity without first catching the disease.

4No vaccination, or only a few vaccinated: the pathogen keeps passing easily between people.

5Most people vaccinated: the pathogen is less likely to reach the unvaccinated, so they are protected too (herd immunity).

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Worked example

Problem

Two towns face the same pathogen. In town A, only a few people are vaccinated. In town B, most people are vaccinated. Each town has one person who is unable to be vaccinated. In which town is that person more likely to be protected? Explain your answer.

⚠ Watch out

Saying the vaccine contains antibodies. It contains a dead or inactive form of the pathogen, and the white blood cells produce the antibodies. And don't stop there: the protection comes when the same pathogen re-enters and the white blood cells respond quickly with the correct antibodies.

🧠

Memory hook

Meet it dead, beat it fast. Vaccinate the most to help shield the rest.

✓

Check yourself

Without looking back, give the five stages from 'vaccine goes in' to 'infection is prevented'. Then finish: 'When most people are vaccinated, someone who can't be vaccinated is protected because…'

Flashcards

(7)

What does a vaccine introduce into the body?

Small quantities of a dead or inactive form of a pathogen.

What does the dead or inactive pathogen stimulate the white blood cells to do?

Produce antibodies.

After vaccination, what happens if the same pathogen re-enters the body?

The white blood cells respond quickly to produce the correct antibodies, preventing infection.

What can vaccination make a person, without them first having to catch the disease?

Immune to that pathogen.

What happens to a pathogen in a population where nobody, or only a few people, are vaccinated?

It can keep passing easily between people.

Why does vaccinating most people protect someone who can't be vaccinated?

Fewer people can pass the pathogen on, so it is less likely to reach them.

What is herd immunity, and what does it need?

Protection for those who can't or won't have the vaccination. It needs a high proportion of the population to be vaccinated.

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

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Who does it protect?

Explain it in your own words

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