D5: The immune system — A level

Experiment with this epidemic and vaccination simulator. Only change the immunisation rates and the “same as left” checkbox.

Notes:

• The immunisation rate is a decimal - multiply by 100 to get a percentage.
• The “same as left” checkbox allows you to split the population into left and right halves that have different immunisation rates.
• Once you have set up your immunisation rates, click “repopulate” to set up the population.
• Click one of the red or green “O”s to infect the first person. Then watch how the disease spreads.

Notice that some immunised people still get infected and are able to transmit the disease to someone else.

Write down what you have noticed about the transmission of a disease. Use these points to guide you.

• What is the relationship between immunisation rate and the number of people who get infected?
• Can you always prevent infection from spreading?
• Herd immunity means that enough people are immunised to prevent the disease from spreading through a community. This protects the small number of people who are unable to be immunised for some medical reason. What immunisation rate produces herd immunity, in your opinion?
• What happens when one side has a high vaccination rate (say, 0.9), and the other side has a low immunisation rate (say, 0.5)?

Make some kind of conclusion about the importance of immunisation.