SARAH: Back in the early 1700's the British employed for the first time a vaccine against a disease. Germs of the smallpox virus were introduced into the body to stimulate the immune system.

RALPH: These people were said to to be inoculated. At that time, as well as in Shakespeare's, to inoculate meant to graft one type of plant onto another.

SARAH: The word comes from the image of placing a tiny bud into the center of a larger plant — putting an eye, or, in Latin, occulus, in the other organism, that is to,  in-oculate.

RALPH: Although this practice only started in England in the 18th century, the Chinese were inoculating against smallpox well before Shakespeare was born.