This book explores how vaccines work and are developed, highlighting examples of historic vaccines and the diseases they help prevent as well as the debates and challenges related to vaccination that remain today. The book also includes a table of contents, two infographics, informative sidebars, two Case Study special features, quiz questions, a glossary, additional resources, and an index. This Focus Readers title is at the Voyager level, aligned to reading levels of grades 5-6 and interest levels of grades 5-9.