In this two-part lesson students explain the role of science in informing public policy. In Part I, students discuss their prior knowledge of vaccinations and the purpose of vaccinations. In Part II, students assume the roles of members of Congress to determine if they will support a bill to require the federal government to compare the health outcomes of vaccinated and unvaccinated children. Students use primary sources to explore the issue and then will work in small groups to discuss the most important factors affecting Congress’s decision. Finally, students interview an adult about their knowledge and opinion of science and public policy, particularly related to vaccinations.