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BBiologyMathematicsS4 to S6Medicine · Health
Epidemic lab: how a disease spreads and how vaccines stop it
How do health workers decide how many people to vaccinate? Run an outbreak in a town of 100 000 people and discover herd immunity.
LevelS4 to S6 (and A Level, IB)
TimeAbout 40 min
You useModels, exponential growth, percentages
PriceFree: no account
🎯 Aim
To use an SIR model to study how an infectious disease spreads, and how vaccination and hygiene reduce or stop an outbreak.
You will learn to
- Explain R₀ and the effective reproduction number.
- Describe exponential growth at the start of an outbreak.
- Calculate the herd immunity threshold 1 − 1/R₀.
- Explain how vaccination and hygiene change the curve.
🧭 What to do
- Read the graph for R₀ = 3: when is the peak?
- Move the day slider under the graph and watch the people.
- Increase R₀: what happens to the peak and the total?
- Increase Vaccinated before the outbreak until the outbreak stops.
- Try Hand washing, masks and staying home when sick. Answer the questions.
- Write your conclusion and download your lab report.
📋 The data
Example weekly cases in an outbreak (made for learning, not official figures).
🧠 Investigate: answer from the data
Type your answer and tap Check. Use 💡 Hint first; open the method only when you are stuck.
➕ Get more from this experiment
📝 Free
Print the worksheet (button above), download the data, and save your report. Teachers can project this page in class.
📦 Premium Lab Pack
1 000 RWF
- Worksheet: modelling an outbreak with a table and a calculator
- Vaccination and herd immunity problems
- Teacher guide and answer key
- Exam-style questions with marking scheme
👩🏫 For teachers
Use it as a practical when apparatus is missing, as homework, or as a project. Free lesson plans help you plan, teach and assess.
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