AQA Biology 4.3.1.7

Vaccination

A vaccine gets your white blood cells ready. See it work in one person, then across a whole population.

Combined Science · Foundation tier

Start here

Chickenpox, once.

Most people only catch chickenpox once, even though they meet it again and again later in life.

If you had to guess, is that because your body remembers it, or because the germ can’t get back in?

How a vaccine works

Ready before it arrives.

A vaccine contains small quantities of dead or inactive forms of a pathogen. These stimulate white blood cells to produce antibodies. Some of these white blood cells stay in the body as memory cells. If the same pathogen re-enters the body, the white blood cells respond quickly to produce the correct antibodies, preventing infection. Compare the two people.

Meeting the pathogen for the first time, white blood cells take time to make the right antibodies. Meanwhile the pathogen multiplies, and you become ill.

Antibodies are specific: a vaccine protects against one pathogen. The flu virus changes, so a new flu vaccine is made each year.

Vaccinating a population

Break the chain.

If a large proportion of the population is immune to a pathogen, the spread of the pathogen is very much reduced. This is called herd immunity. Set how many people are immune, then watch one infected person arrive.

0 of 25 people infected. Few people are immune, so the pathogen spreads to almost everyone.

Reading the evidence

Before and after a vaccine.

The graph shows cases of a disease each year in one country. A vaccine was introduced in year 5. What does it show?

Pick one.

Think again · what’s in a vaccine?

“The vaccine has antibodies in it.”

Your call

Choose

What does a vaccine contain?

Sort

Does it happen?

Place each statement.

Tap a card, then tap the box it belongs in. Tap a placed card to take it back.

Command words in this lesson

Explain: How a vaccine prevents illness, link by link.
Describe: A graph of cases before and after a vaccine.
Evaluate: Whether data show a vaccine worked.

Key fact

A vaccine stimulates white blood cells to make antibodies. If the pathogen returns, they respond quickly, preventing infection.

Key note · AQA 4.3.1.7

Vaccination

A vaccine contains small quantities of dead or inactive forms of a pathogen.
It stimulates white blood cells to produce antibodies.
If the same pathogen re-enters, white blood cells respond quickly to produce the correct antibodies, preventing infection.
If a large proportion of the population is immune, the spread of the pathogen is very much reduced.

Photograph this card. Tomorrow, cover it and say each line first.

Previous and next

Connects to

White blood cells and defences

Ask MrBadmus

Not sure why vaccinating most people protects the rest?

The cases graph and the population grid are made-up teaching data.