CASE STUDY According to the Centers for Disease Control and Prevention (CDC), there were 173 cases of measles reported between June 1 and May 29, 2015. About 87% of the cases were related to five outbreaks during the same time period. The CDC also reported that the “United States experienced a record number of measles cases during 2014, with 668 cases from 27 states reported to CDC’s National Center for Immunization and Respiratory Diseases (NCIRD). This is the greatest number of cases since measles elimination was documented in the U.S. in 2000.” According to the same report by the CDC, “the majority of people who got measles were unvaccinated.“ Vaccinating children against diseases like measles is controversial.

The debate about childhood vaccinations became a major news issue in late 2014 and early 2015. As of June 2015, Mississippi and West Virginia are the only two states that require vaccines for children with only medical exemptions. California may become the third state. Other states allow exemptions for personal and religious beliefs. A Gallup Poll conducted from February 28–March 1, 2015, asked the following question: “How important is it that parents get their children vaccinated—extremely important, very important, somewhat important, or not at all important?” The Gallup Poll found that 54% of respondents said “extremely important” (down from 64% who responded to a similar 2001 Gallup Poll). Can we trust this conclusion?

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Reading further, we find that Gallup talked with 1015 randomly selected adults to reach these conclusions. We’re happy Gallup chooses at random—we wouldn’t get unbiased information about the importance of childhood vaccinations by asking people attending a conference of the American Medical Association. However, the U.S. Census Bureau said that there were about 258 million adults in the United States in 2013. How can 1015 people, even a random sample of 1015 people, tell us about the opinions of 258 million people? Is 54% who feel that it is extremely important for parents to get their children vaccinated evidence that, in fact, the majority of Americans feel this way? By the end of this chapter, you will learn the answers to these questions.