The SIR Epidemiology Model in Predicting Herd Immunity

by Joanna Nicho

Submitted : Spring 2010

The Simple Epidemic Model uses three states to describe the spread of an infection, the susceptible (S), the infected (I), and the recovered (R). This model can predict the trend that will be seen of the infection over time. It can also be used to predict whether an infection can spread. This is important in epidemiology because it allows epidemiologists to predict the percentage of the population that needs to be vaccinated in order to provide herd immunity. While most parents allow their children to be immunized, some are hesitant because of false beliefs. One in particular is that the Measles, Mumps, and Rubella vaccine can cause autism. No scientific data has been found to support this yet some parents have gone as far as to refuse the vaccination because of this belief. The study will compare the percentages required for herd immunity to the number of people that may decide not to vaccinate their children.

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