French Chemist Louis Pasteur

In 1881, Louis Pasteur publicly demonstrated the effectiveness of his Anthrax Vaccine in a famous experiment that helped solidify his place as a pioneer in microbiology and immunology.

Context:

By the late 19th century, anthrax was a major problem for livestock, killing thousands of sheep and cattle across Europe. Pasteur had already developed a theory that weakened (attenuated) microbes could be used to create immunity in animals—a principle he previously tested with chicken cholera.

The Experiment: Pouilly-le-Fort, France (May–June 1881)

• Location: A farm in Pouilly-le-Fort, near Melun, France

• Organized by: Pasteur, at the request of veterinarians and local officials who were skeptical of his work and wanted a public test

• Purpose: To prove that vaccination with an attenuated strain of Bacillus anthracis could protect animals from anthrax

Setup:

• Total animals: 50 sheep

• Group A (vaccinated): 25 sheep were vaccinated with Pasteur's attenuated anthrax vaccine in two doses (on May 5 and May 17)

• Group B (unvaccinated control): 25 sheep received no vaccine

• On May 31, all 50 sheep were injected with a lethal dose of live anthrax bacteria

Outcome (June 2, 1881):

• All 25 vaccinated sheep survived

• 24 of 25 unvaccinated sheep died (1 may have died from another cause or was slow to succumb)

This dramatic and very public success received widespread media coverage and was a major step forward in gaining acceptance of germ theory and vaccination.

Scientific Significance:

• Demonstrated the effectiveness of attenuated vaccines

• Helped promote the idea that specific microbes cause specific diseases, supporting Robert Koch’s work on anthrax as well

• Boosted public and scientific trust in vaccination science

Notes:

• Although Pasteur took credit for developing the anthrax vaccine, some of the preparatory work was carried out by his collaborators, including Chamberland and Roux

• There has been historical debate about whether Pasteur used Koch’s methods or a chemically attenuated culture rather than a heat-attenuated one as he publicly claimed