Medicine has come a long way over the years. The development of the vaccine kicked off an era of illness prevention unlike anything the world had ever seen. In fact, vaccinations are largely viewed as the most successful medical advancement in the history of public health. Before vaccines were introduced, smallpox killed millions, nearly 20,000 were paralyzed by polio, and rubella (German measles) caused serious birth defects in about 20,000 newborns.­

Photo courtesy Children's Healthcare of Atlanta Vaccines have prevented millions of deaths around the world.

In this article, we'll learn about the inspiration for vaccines, the basic science behind how they prevent illness and the diseases they keep at bay. We'll also go head-to-head with some of the common myths circulated about vaccines.

The Inspiration for Vaccines
Who knew that cows would save the lives of countless humans? In 1796, a physician named Edward Jenner decided to prove a theory that had been circulating for some time. Smallpox once killed millions of people worldwide. Cowpox was a less serious disease related to smallpox that milkmaids often caught through exposure to infected cows. Jenner noticed that milkmaids who had contracted cowpox were later immune to smallpox. Jenner tested this theory when he took some infected cowpox matter and exposed an otherwise healthy boy through a cut in his arm. After the boy caught and recovered from cowpox, Jenner exposed him to smallpox via an injection. The boy remained healthy, and the world's first vaccine was born. The cows, for their part, were honored when the term "vaccine" was coined -- "vacca" is Latin for cow. According to the national Centers for Disease Control and Prevention (CDC) the world's last case of naturally occurring smallpox was in 1977. The disease has since been eliminated from natural occurrences in the world, so the vaccine is no longer given.

Vaccine-preventable Diseases
Anthrax	Cervical Cancer	Diphtheria
Hepatitis A	Hepatitis B	Haemophilus influenzae type b
Human Papillomavirus	Influenza	Japanese encephalitis
Lyme disease	Measles	Meningococcal
Monkey pox	Mumps	Pertussis
Pneumococcal	Polio	Rabies
Rotavirus	Rubella	Shingles
Smallpox	Tetanus	Typhoid
Tuberculosis	Varicella	Yellow Fever
Source: CDC

­On the next page, we'll learn about how vaccines work in your body to destroy diseases.