Following the invention of the smallpox vaccine, Louis Pasteur began investigating the potential for other vaccines. Pasteur chose to study chicken cholera, isolating and culturing the causative organism, Pasteurella multocida, in 1877. In 1879, through an accident, Pasteur discovered that the bacteria declined in virulence over time by injecting the less virulent cholera into chickens. After being injected, these chickens recovered easily and did not become sick when injected with highly virulent cholera bacteria. He called the process of decreasing virulation in a laboratory attenuation. Attenuation was done using heat, exposure to oxygen, or serial cultivation in a medically significant species depending on the causative agent.

Pasteur and others went on to use attenuation to produce vaccines against anthrax in sheep and cows, against rabies in humans, and more. Attenuation was the method used for the creation of vaccines through much of the 20th century. Pasteur’s discovery revolutionized the field of medicine for years to come. Haimabati Sen’s life was often defined by illness whether she was treating it or inflicted with it. Many of these illnesses would later be preventable through vaccines developed through attenuation.

SOURCES

https://www.historyofvaccines.org/content/first-laboratory-vaccine

https://www.vbivaccines.com/evlp-platform/louis-pasteur-attenuated-vaccine/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4151719/

https://media.nature.com/original/magazine-assets/d42859-020-00008-5/d42859-020-00008-5.pdf