Vaccines are crucial to maintaing public health: They are a safe, cost effective, and efficient way to prevent sickness and death from infectious disease. Vaccines have led to some of the greatest public health triumphs ever, including the eradication of naturally occurring smallpox from the globe and the near eradication of polio. The booklet contains general information about vaccines such as what they are, how they prevent disease, how they are made and tested, and what vaccine research might achieve in the future.