The Pasteurian contribution to the history of vaccines.

Vaccination, the transmission of "vaccine", a benign disease of cows, to immunize human beings against smallpox, was invented by Jenner at the end of the eighteenth century. Pasteur, convinced that the vaccine microbe was an attenuated form of the smallpox microbe, showed that, similarly, attenuated forms of other microbes immunized against animal diseases. When applying this principle to rabies, he realized that, in this case, the vaccine was in fact composed of dead microbes. One of his students immediately exploited this result to devise a vaccine against typhoid. The vaccines against diphtheria and tetanus, in 1921, opened a new route, that of immunization with molecules from the pathogenic microbes. Molecular biology then allowed the production of the immunogenic molecules by microorganisms such as yeast, or immunization by genetically modified viruses or messenger RNA inducing our own cells to produce these molecules.