School › Vaccines › Ages 10–11
How vaccines work
What is inside a vaccine, how it trains white blood cells to make antibodies and memory cells, why some vaccines need several doses, and how vaccinating many people protects everyone. With a herd immunity fair test.
Read
A vaccine works by imitating an infection. Its active ingredient is an antigen: weakened or killed germs, pieces of their surface, or a germ's poison (toxin) made harmless.[1]
Some newer vaccines carry instructions (DNA or RNA) that tell the body's own cells to make the antigen.[2]
The immune system reacts as it would to the real germ, but without the disease: white blood cells multiply and make antibodies, proteins that recognise that germ.[2][1]
Afterwards, memory cells stay in the body. If the real germ arrives, they respond faster and more strongly.[2]
Protection takes weeks to build up, and one dose often gives only partial protection, so many vaccines are given in several doses, weeks or months apart.[1][2]
Every vaccine is tested before use and monitored afterwards. Common side effects are a red, sore arm for 2 to 3 days or a high temperature for 1 or 2 days.[3]
When enough people are immune, a disease can no longer spread: this is herd immunity. It helps protect people who cannot have a vaccine. No vaccine gives 100% protection.[7][2]
In 1796 Edward Jenner put material from a cowpox sore into 8-year-old James Phipps: the first vaccine, against smallpox. Smallpox killed at least 1 in 3 people who caught it, and in 1980 the WHO declared it eradicated.[6]
Try it: Can vaccines stop a spread?
You need
- A 5 × 5 grid of 25 squares drawn on the board or on paper (one square per 'person')
- Counters in two colours ('vaccinated' and 'caught it')
- A die
- Results table
Safety
This is a paper model. Nobody plays a 'germ' or is labelled as ill, and pupils should not be asked about their own vaccinations.
What to do
- Use the same grid and the same starting square (the middle one) for every run: that keeps the test fair.
- Run 1: no one is vaccinated. The starting square has 'caught it'. Each 'caught it' square passes it to every square that touches its sides, unless that square is vaccinated. Keep going until nothing new happens. Count the squares that caught it.
- Run 2: roll the die for each square; a 5 or 6 means 'vaccinated' (about 1 in 3). Repeat the spread and count.
- Run 3: now a 3, 4, 5 or 6 means 'vaccinated' (about 2 in 3). Repeat and count.
- Do each run three times, find the mean and compare. What changed when more squares were vaccinated?
What happens, and why?
With no one vaccinated, the 'germ' reaches everyone. As more squares are vaccinated, they block the paths between squares, so the spread stops sooner and even unvaccinated squares can stay safe. This is the idea of herd immunity. The grid is only a model: real vaccines are not 100% effective and real people mix in more complicated ways.[7][2]
Play: Fact or myth?
Read each statement about vaccines. Is it a fact or a myth? Pick the right box.
Your best score is kept only on this device. Nothing is sent anywhere.
Quiz
Other ages: Ages 6–7 · Ages 15–16