The development of vaccines is one of the most important breakthroughs in the history of medicine. Mere decades ago, diseases like smallpox, polio and diphtheria spread throughout the world with devastating results. People died, were paralyzed, crippled and disfigured by diseases that today, are preventable through vaccination. Several of these dreadful diseases are practically eradicated in the developed world and elsewhere, good progress is being made to reduce their spread. Indeed, successful vaccine development has played a vital role in preventing the huge burden of infectious diseases and their complications in developed countries and in raising the living standards and life expectancy of peoples in the developing world.

In the past, any number of infectious diseases could decimate a herd or flock of domesticated animals. Today, vaccines that protect animals are vital for raising livestock essential for world food production and our quality of life. Some of the first vaccines were developed to protect food-producing animals against disease. These veterinary vaccines also protect people from diseases because many animal diseases are transmissible to humans.

In the last ten years, new discoveries and ideas have led to breakthroughs in the way we approach vaccine sciences. Today, Americans are at the dawn of a new era in vaccine research. Genetic engineering has allowed scientists to create new vaccines with greater potential for protecting both humans and animals. Researchers are also hard at work developing vaccines to control certain existing and emerging infectious diseases, to protect populations against bio-terrorism, to treat cancers, and to attack other illnesses, such as Alzheimer's disease.

But what is a vaccine, really? What do vaccines do? What is the role of animals in vaccine development? And what does the future hold?