ABSTRACT
Vaccination or immunization against infections predates chemotherapy as a method for the control of infectious diseases. By the 5th century B.C., in Greece, it was well known that recovery from infection with smallpox or plague rendered individuals resistant to reinfection and that this resistance was specific. Nobody knows when the practice of immunization began, but over 2500 years ago the Chinese were known to inhale a powder made from smallpox scabs to protect them from this disease and by the 17th century, and probably earlier, the injection of material from active lesions as a prophylactic measure against smallpox was widespread and well documented in the Middle East. A similar kind of immunization against cutaneous leishmaniasis dates from the same period, and variations of this procedure persist to the present day. This empirical approach became scientifically acceptable with Jenner’s famous experiments in which he used cowpox, vaccinia, material to protect individuals against smallpox; ever since, the word vaccination has been used to describe immunization procedures.
