People have long had the feeling that there must be something that transmits disease from person to person and from the exterior from the experience during plagues and the like. One disease that was particularly deadly was small pox and people had tried to inoculate themselves with material from diseased persons for protection. There are stories from India, China and Asia Minor concerning vaccinations.
The name however, derives from latin for cow, "vacca", because of Edward Jenner's (1743-1829) discovery 1796 that a person that had had cow pox, a milder disease than small pox, might be immune to the real killer. It should be noted that people had been inoculated against the disease earlier and that a letter was submitted to the Royal Society of London in 1724 about the practice of inoculating with real small pox material, a rather more dangerous practice however. Small pox was deadly in 20-30% of cases and accounted for 8-20% of deaths in the 18th century.
Another clear cut evidence that something small was causing child birth fever that was highly deadly in the 19th century Europe was Ignaz Semmelweis' 1847 discovery that he could lower the deaths significantly with introducing hand hygiene in doctor's wards relative wards of midwives. His results where not taken seriously, however, before Louis Pasteur laid down the germ theory between 1860 and 1865. It is interesting that Antonie van Leeuwenhoek's discovery 1676 of bacteria from the mouth was not vigorously followed up and that microbiology did not develop during the 18th century rather than during the 19th century.
Louis Pasteur (1822-1895) is considered one of the three main founders of microbiology, the other two being Ferdinand Cohn (1828-1898) and Robert Koch (1843-1910). Pasteur was born in Dole situated in the Jura region of France in a family of a poor tanner. He gained degrees in Letters and Mathematical Science before entering an elite College, École Normale Supérieur. He became professor of chemistry at the University of Strasbourg 1848. He married Marie Laurent, the daughter of the University rector in 1849. In his early career as a chemist he for the first time described chirality.
However, Pasteur was to become most famous as a microbiologist by firmly establishing the germ theory together with Robert Koch and others. He managed to convince Europe about this theory which had profound effects on the possibility for people to protect themselves against disease. Pasteurization of liquids, especially milk, in 1862 was such an example. Pasteur demonstrated that fermentation was cause by microorganisms and that the theory of spontaneous generation was wrong, ie, fermentation came from the exterior to, for example, a broth solution.
Pasteur also produced the first weakened rabies vaccine from dried spinal cords of infected rabbits. A college of his, Émile Roux, a French physician, worked with the vaccine on only eleven dogs before it was tested on a 9 year old boy that had been bitten by a rabid dog 1885 and who would most probably have been killed by rabies if untreated. The vaccination, which in the case of rabies is therapeutic, worked and the boy's life was saved.
This and Jenner's cow pox vaccination were performed despite the fact that viruses where not yet known. The first known virus, tobacco mosaic virus, was to be discovered in 1892 by the Russian Dimitry Ivanovsky. He used a filter invented 1884 by the French microbiologist Charles Chamberland called the Chamberland-Pasteur filter. Viruses are too small to be seen by an ordinary microscope.
Louis Pasteur was a man of faith. He wrote, for example: "Happy the man who bears within him a Divinity, an ideal of beauty and obeys it, and ideal of art, and ideal of science, an ideal of country, an ideal of the virtues of the Gospel." He was puzzled by the failure of scientists to not recognize God's existence from their observations of the world around them.
Data from Wikipedia