Louis Pasteur (1822–1895) may be best known for developing the process that bears his name, pasteurization, but the French chemist and microbiologist made other important contributions to public health, including the discovery of vaccines to prevent diseases in animals and the establishment of a Paris institute for the study of deadly and contagious diseases.

In the 1860s the hard-working Pasteur was asked to investigate problems that French winemakers were having with the fermentation process: Spoilage of wine and beer during fermentation was resulting in serious economic losses for France. Observing wine under a microscope, Pasteur noticed that spoiled wine had a proliferation of bacterial cells that produce lactic acid. The chemist suggested gently heating the wine to destroy the harmful bacteria, and then allowing the wine to age naturally. Pasteur published his findings and his recommendations in book form in 1866. The idea of heating edible substances to destroy disease-causing organisms was later applied to other perishable fluids—chief among them milk.

Pasteur later studied animal diseases, developing a vaccination to prevent anthrax in sheep and cattle. The deadly animal disease is spread from animals to humans through contact or the inhalation of spores. In 1876 German physician Robert Koch (1843–1910) had identified the bacteria that causes anthrax, and Pasteur weakened this microbe in his laboratory before injecting it into animals, which then developed an immunity to the disease. He also showed that vaccination could be used to prevent chicken cholera.

In 1881 Pasteur began studying rabies, an agonizing and deadly disease spread by the bite of infected animals. Along with his assistant, Pierre-Paul-Émile Roux (1853–1933), Pasteur spent long hours in the laboratory, and the determination paid off: Pasteur developed a vaccine that prevented the development of rabies in test animals. On July 6, 1885, the scientists were called on to administer the vaccine to a small boy who was bitten by a rabid dog. Pasteur hesitated to provide the treatment, but as the boy faced certain and painful death from rabies, Pasteur proceeded. Following several weeks of painful injections to the stomach, the boy did not get rabies: Pasteur’s treatment was a success. The curative and preventive treatments for rabies (also called hydrophobia) we know today are based on Pasteur’s vaccination, which has allowed officials to control the spread of the disease.

In 1888 the Institut Pasteur was established in Paris to provide a teaching and research center on contagious diseases; Pasteur was director of the institute until his death in 1895.