4The COVID-19 pandemic has raised important questions about how we fight germs: How do vaccines work? Can wearing a mask really stop diseases from spreading? How do diseases spread in the first place? These questions aren't new, but they're an important part of life today. And readers discover the answers to them in this detailed look at the fight against germs. The objective main text is supplemented with sidebars, graphic organizers, and full-color photographs. In addition, readers find critical thinking questions at the end of each chapter to help them develop informed opinions about this important issue.