How many people do we need to vaccinate?

1
How many people do we need to vaccinate?

• Reproductive Ratio

Measles R0 12 to 18 Mumps R0 4 to
7 Rubella R0 5 to 7
2
Suppose R0 10

• How many new infections result from each infected
  person on average?
• 10
• So how many people do we need to vaccinate to
  reduce R0 to 1 or less?
• 9
• What proportion of the population do we need to
  vaccinate therefore?
• 90

3
Suppose R0 20

• How many new infections result from each infected
  person on average?
• 20
• So how many people do we need to vaccinate to
  reduce R0 to 1 or less?
• 19
• What proportion of the population do we need to
  vaccinate therefore?
• 95

4
Suppose R0 5

• How many new infections result from each infected
  person on average?
• 5
• So how many people do we need to vaccinate to
  reduce R0 to 1 or less?
• 4
• What proportion of the population do we need to
  vaccinate therefore?
• 80

5
Suppose R0 r

• How many new infections result from each infected
  person on average?
• r
• So how many people do we need to vaccinate to
  reduce R0 to 1 or less?
• r - 1
• What proportion of the population do we need to
  vaccinate therefore?