Discoveries of Edward Jenner and Louis Pasteur. Some of the early discoveries that led to today’s vaccines happened almost by chance. The astute observations of Jenner and Pasteur were the foundation of immunology.
Edward Jenner and the First Vaccine (1790s)
The Dreaded Smallpox
Edward Jenner’s legacy was a vaccination for smallpox; a disease greatly feared during his lifetime. Smallpox killed a third of those who caught it and the individuals who did survive were often badly disfigured.
Old Wives Tales of Immunity
Jenner was a physician who practiced in the rural English countryside. Being a country doctor, he was familiar with the region’s medical “old wives tales,” one of which was that milkmaids who had caught cowpox never became infected with the more serous smallpox.
Cowpox and Smallpox
Cowpox was a mild disease evidenced by discomfort, aching, pustules, some swelling; symptoms that only lasted a few days. In contrast, smallpox was a very serious disease that resulted in massive disfigurement, sometimes blindness, and often death.
Jenner’s First ‘Vaccine’
Jenner suspected there to be a connection between the fact that milkmaids were commonly known to get cowpox, but not smallpox. He decided to test this theory by placing the scab from a cowpox lesion into a cut made in the arm of a young man. He then deliberately injected his human guinea pig with smallpox. The infected young man became ill, but after a few days made a full recovery with no side effects.
Laughing Stock Who Had the Last Laugh
At first his peers doubted the safety and efficacy of his treatment, and he was publicly humiliated when he presented his findings in London. But eventually the value of the cowpox inoculum could not be denied and Jenner’s discovery changed the world.
Pasteur’s Attenuated Vaccines (1870s)
Fowl Cholera of Chickens
Physicians of the time observed that individuals who recover from an infectious disease are sometimes immune from future attacks. This knowledge prompted Louis Pasteur, a French biologist and chemist, to try to find a way to prevent fowl cholera, an infectious disease of chickens.
Microbes in the Laboratory
Pasteur understood that different microorganisms were associated with different diseases, and had learned how to grow some of them in the laboratory; purposefully infecting animals in order to study the disease.
Discovery through Neglect
When a colleague of Pasteur’s postponed inoculations of cholera into a group of chickens, a remarkable discovery resulted. The cholera, which had been left to grow under laboratory conditions for an extended time, no longer could cause the disease. Instead, inoculation with these neglected cultures made the chickens immune to fowl cholera.
By leaving the microbes uncared for in the laboratory media for an extended period of time, the organisms had been weakened or attenuated. Pasteur concluded that inoculation with weakened microbes could render immunity to the disease that that particular microbe caused.
Anthrax and Rabies Vaccines
Pasteur then experimented with modifying other organisms such as anthrax, and the virus causing rabies. Ultimately, through his experimentation he created the inoculation procedures of acquired immunity–what we now know as vaccinations.