Vaccines are biological substances that cause the human immune system to build up its defenses against specific diseases. Public health officials recommend a series of vaccines for all children, as well as some vaccines for teenagers and adults. But not everyone gets the vaccines they need. Many poor nations don''t have the resources to deliver vaccines to every community. Some parents refuse to have their children vaccinated because they don''t believe the evidence proving that vaccines are safe.The effort to wipe out diseases using vaccines continues. Vaccine Investigation recounts the fascinating history of vaccines, their important role in protecting community health, and the excitement of cutting-edge research.