Effect of Immunity and Susceptibility on Sickness or Mortality Risk

risk model

linear

sigmoid

double sigmoid

all models' parameters

p

0

0.4

p

min

0.1

p

max

0.7

sigmoid model's parameter

c

5.

double-sigmoid model's parameters

x

c

1

-0.5

m

1

8.

x

c

2

0.5

m

2

6.

x

0.6

linear risk model

x (index) = 0.60

p

0

(uncorrected risk) = 0.40

y (corrected risk) = 0.58

The probability that a person becomes ill or dies of ingested biological or chemical agents is usually estimated from the agent's dose-response curve. Such estimation does not take into account the individual's immunity or susceptibility state. This state can be represented by an index,

x

, for example,

-1≤x≤1

, where the lowest value represents extreme immunity and the highest extreme susceptibility. A correction function,

p(x)

, can be used to convert the nominal risk,

p

0

, expressed as the probability of becoming sick or dying according to the agent's dose-response curve, into a more realistic individual risk. The concept is demonstrated with three hypothetical correction modes based on linear, sigmoid, and double-sigmoid models.