Refer to the graph below to respond to the following prompts.

A line graph depicting measles cases in the United States between 1944 and 2007. The y-axis is labeled cases (thousands) and starts at the bottom at 0 and moves up in intervals of 100 until it ends at 800. The x-axis is labeled years and starts at the left at 1944 and moves to the right at intervals of 10 years, ending on the far right at 2004. The first point in the graph is approximately 610 (y-axis) and 1944 (x-axis). The graph then spikes up and down for many years until 1964 (y-axis) where the point is labeled vaccines licensed and the y-axis is at approximately 400. The last point in the data is 0 (y-axis) and 2004 (x-axis).
Public Domain

Part 1: Based on the information presented in the graph, describe the correlation between measles cases and vaccine coverage. Cite data from the graph to support your answer.
Part 2: A classmate is having trouble understanding how vaccines provide immunity. Using what you have learned in the lesson, write an explanation to share with your classmate about how vaccines work with your immune system to protect you against infection.