In the first half of the 20th century, whooping cough was a frequently occurring bacterial infection that often resulted in death, especially among young children. A vaccination for whooping cough was developed in the 1940s. How effective has the vaccination been in eradicating whooping cough? One measure to consider is the incidence rate (number of infected individuals per 100,000 populations) in the United States. The table shows incidence rates from
1925 €“ 1970.
Incidence Rates for Whooping Cough, 1925€“1970
Year Rate per 100,000
1925.......... 131.2
1930.......... 135.6
1935.......... 141.9
1940.......... 139.6
1945.......... 101.0
1950.......... 80.1
1955.......... 38.2
1960.......... 8.3
1965.......... 3.5
1970.......... 2.1
Data from Historical Statistics of the United States, Colonial Times to 1970, U.S. Department of Commerce, p. 77.
a. Sketch a time plot. What type of trend do you observe? Based on the trend from 1945€“1970, was the whooping cough vaccination proving effective in reducing the incidence of whooping cough?
b. The figure shown is a time plot of the data from 1980€“1999, reported in the Morbidity and Mortality Weekly Reports (MMWR). 3 What has the incidence rate been since about 1993? How does the incidence rate since 1993 compare with the incidence rate in 1970? Is the United States close to eradicating whooping cough? (Note: In the years 2006€“2008, the incidence rates were 5.27, 3.49, and 4.40 respectively.)
c. Would a histogram of the incidence rates since 1935 address the question about the success of the vaccination for whooping cough? Why or why not?

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Time Plot of Whooping Cough Incidence Rates per 100,000), 1980-1999 4 0 80 85 90 95 Year