Vaccination

Smallpox, once a common viral infection that claimed millions of lives in periodic epidemics around the globe, is now considered fully eradicated. Much of the credit for this medical triumph belongs to the English physician Edward Jenner, who in 1796 developed the first effective vaccine against smallpox. Jenner's discovery laid the foundations for the science of immunology. Vaccines are now used to control and prevent diphtheria, hepatitis, influenza, meningitis, polio, tetanus, typhoid fever, whooping cough, and many other diseases that once plagued humankind.
In Jenner's day a procedure called variolation was used to protect people against smallpox. The procedure involved scratching a bit of the substance from smallpox blisters—obtained from a person with a mild case of the disease—into a healthy person's arm. Hopefully, a mild case of the disease would develop and pass, but the procedure was often deadly.
Jenner, orphaned at the age of five, was born and raised in the tiny English village of Berkeley, near Bristol. At the age of 13, Jenner was apprenticed to a country surgeon. Shortly after, milkmaids told him that after they contracted cowpox, a harmless disease confined usually to their hands and arms, they never got smallpox.
Following his training with the famous surgeon John Hunter in London, Jenner returned to Berkeley and devised an experiment to learn whether cowpox could protect against smallpox. On May 14, 1796, Jenner made two small scratches on the arm of an eight-year-old boy named James Phipps. On those scratches he rubbed fluid from a milkmaid's cowpox blister. Eight days later, Phipps developed small cowpox blisters on the scratches. On July 1 Jenner variolated Phipps with fluid from a smallpox blister. Phipps never got even a mild case of smallpox.
Jenner had made two important discoveries: Cowpox protects against smallpox, and cowpox could be transmitted from person to person. He subsequently vaccinated another eight children, including his own son, experimenting further with his new technique. In 1798 Jenner submitted his findings to Philosophical Transactions, but his work was rejected. After further experiments, he published his results himself, paying for the printing.
Vaccination was initially viewed as unnatural, and the technique encountered significant opposition for decades. More than 80 years passed before Pasteur, drawing on Jenner's work, opened the way for the development of modern preventive vaccines. In the end, however, Jenner received an honorary degree from Oxford University for his groundbreaking work.
source: encarta encyclopedia