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Estimated values of A, L, R0 and PC for different infections and populations.

Infection Place Time

A*

L

R0

PC§

Measles USA 1955-58

5-6

70

13

92%

  India 1978

2-3

55

23

96%

  Senegal 1964

1-2

40

28

96%

Rubella Sweden 1965

9-10

75

8

88%

  Poland 1970-77

6-7

70

11

91%

  Gambia 1976

2-3

40

17

94%

Measles England and Wales 1948-68

4-5

70

16

94%

Mumps England and Wales 1970-82

6-7

73

11

91%

Rubella England 1975-77

9-10

73

8

88%

A: Average age at infection (in years)

L: Expectation of life at birth (in years)

R0: Basic reproductive rate

PC: Critical proportion of vaccination above which the infection can be eradicated

* Source of data: Anderson R, May R. Infectious diseases of humans. Oxford: OUP; 1991. p.51.

Source of data: Demographic Yearbook (various years). New York: United Nations.

Calculation from A and L: R0 = L / A for developed countries (high L), R0 = 1 + L / A for developing countries (low L).

§ Calculation from R0: PC = 1 - 1 / R0.

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Observe the table and discuss possible social and viral characteristics which may relate to different values of A and L. Observe how R0 and PC depend on A and L, and therefore on the social and viral characteristics.

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