Few scientific discoveries have had the impact on the health of the world as have vaccines. The ability to routinely immunize children against many childhood diseases saves millions of lives annually. It has been two hundred years since a country doctor from England named Edward Jenner first discovered a way to vaccinate against the most dreaded disease of that time, smallpox. On May 14, 1796, Jenner applied the first vaccine by using cowpox to immunize James Phipps against smallpox.

A French chemist, Dr. Louis Pasteur, previously noted for his studies of fermentation and bacteria, disproved the theory of spontaneous generation and advanced the germ theory of infection.

Pasteur was able to prove that protection against disease could be afforded by the infection of weakened germs which cause silent and relatively harmless infections. The milestone in immunization for which Pasteur is most noted occurred in 1885. A boy named Joseph Meister was bitten by a rabid dog and, for the first time in history, was successfully treated with a vaccine that prevented the development of rabies

A substance that fights a disease by protecting the body from a virus or bacteria.

Vaccines cause the body to develop antibodies to fight a disease.

A vaccine is made from the antigen—either a bacteria or a virus—that causes the disease. Some vaccines use live but weakened versions of the antigen.

A vaccine does not contain enough of antigens to cause the disease. It has just enough to trigger the body’s immune system to produce antibodies against that disease. In most cases, these antibodies remain active and protective against the disease for a person’s lifetime. This protection is called immunity. In some cases, a vaccine requires booster shots, doses given at regular intervals.