Vaccination refers to a procedure in which the presence of an antigen stimulates the formation of antibodies. The antibodies act to protect the host from future exposure to the antigen. Vaccination is protective against infection without the need of suffering through a bout of a disease. In this artificial process an individual receives the antibody-stimulating compound either by injection or orally.

The technique of vaccination has been practiced since at least the early decades of the eighteenth century. Then, a common practice in Istanbul was to retrieve material from the surface sores of a smallpox sufferer and rub the material into a cut on another person. In most cases, the recipient was spared the ravages of smallpox. The technique was refined by Edward Jenner into a vaccine for cowpox in 1796.

Since Jenner's time, vaccines for a variety of bacterial and viral maladies have been developed. The material used...