Vaccine Scares and Behavior Theory: How Herd Immunity Affects Vaccination Rates

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Health care professionals recommend the influenza vaccine. Photo by Jim Gathany, Centers for Disease Control and Prevention.

Why do people still avoid getting vaccinated?

Vaccinations have prevented countless deaths, illnesses, and outbreaks of various diseases over the years. However, some people worry about any potential risk that maybe associated with vaccinations, and have chosen not to get vaccinated. When some people are not vaccinated, this provides an opportunity for disease outbreaks  due to a lack of a phenomenon called ‘herd immunity.’

Medical and public health professionals try to understand and predict what people may do when in comes to a disease outbreak so that they can best communicate the importance of vaccines and provide education. A person’s behavior can be hard, if not impossible to predict, but Dr. Chris Bauch from the University of Guelph in Ontario Canada has developed a behavior-incidence model to predict behavior regarding vaccination scares.

Predicting Vaccination Scare Behavior: A Study

In their study, “Evolutionary Game Theory and Social Learning Can Determine How Vaccine Scares Unfold” Dr. Bauch and colleagues developed a behavior model based on mathematics, game theory, and social learning. They tested their mathematical model on two previous disease outbreaks in England and Whales: the 1970s pertussis outbreak and the measles-mumps-rubella outbreak in the 1990s. The behavior-incidence model showed that in some circumstances it could predict vaccine coverage and disease incidence up to 10 years in advance.

How Does the Behavior-Incidence Model Work?

Dr. Chris Bauch best explains his behavior-incidence model in an interview with Decoded Science.

“The behaviour-incidence model works best because it captures the features of real populations that determine vaccine coverage and disease outbreaks: it captures how individuals learn their behaviour from others, how they take into account the amount of disease currently circulating in the population, and how the disease itself spreads in the population and responds to vaccine programs.  All of these factors are shown to be important for determining how vaccine coverage evolves during a vaccine scare.  The model works through its equations that mathematically predict future disease incidence, vaccine coverage, and how the two are coupled to one another.  The equations themselves are in the same class as the types of equations used in physics to predict the motion of objects, except here we are predicting vaccine coverage and disease incidence instead of the motion of billiard balls.  We fitted the model to empirical data from real vaccine scares to see if the model could explain the patterns observed in the data.”

Click to Read Page Two: What is Herd Immunity?

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© Copyright 2012 Janelle Vaesa, MPH, All rights Reserved. Written For: Decoded Science

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