1. How many people do we need to vaccinate?

2. Suppose R 0 = 10 How many new infections result from each infected person on average? 10 So how many people do we need to vaccinate to reduce R 0 to 1 or less? 9 What proportion of the population do we need to vaccinate therefore? 90%

3. Suppose R 0 = 20 How many new infections result from each infected person on average? 20 So how many people do we need to vaccinate to reduce R 0 to 1 or less? 19 What proportion of the population do we need to vaccinate therefore? 95%

4. Suppose R 0 = 5 How many new infections result from each infected person on average? 5 So how many people do we need to vaccinate to reduce R 0 to 1 or less? 4 What proportion of the population do we need to vaccinate therefore? 80%

5. Suppose R 0 = r How many new infections result from each infected person on average? r So how many people do we need to vaccinate to reduce R 0 to 1 or less? r - 1 What proportion of the population do we need to vaccinate therefore?