A Shot in the Arm! explores the history of vaccinations and the struggle to protect people from infectious diseases, from smallpox—perhaps humankind’s greatest affliction to date—to the COVID-19 pandemic. Highlighting deadly diseases such as measles, polio, rabies, cholera, and influenza, Brown tackles the science behind how our immune systems work, the discovery of bacteria, the anti-vaccination movement, and major achievements from Lady Mary Wortley Montagu, who popularized inoculation in England, and from scientists like Louis Pasteur, Antonie van Leeuwenhoek, and Edward Jenner, the “father of immunology.” Timely and fascinating, A Shot in the Arm! is a reminder of vaccines’ contributions to public health so far, as well as the millions of lives they can still save.