In 1796, an English surgeon noticed that milkmaids rarely got smallpox, and the vaccination changed the world

Edward Jenner’s account of his discovery of the vaccine does not involve a lab filled with new gadgets or an amazing medical breakthrough; it came while he was observing the activities of milkmaids in the dairy regions of England in the late eighteenth century. For many years, rural people noted that women who got cowpox, a mild infection transmitted to humans from infected cows, had much less chance of contracting smallpox.

The observation made Jenner realize that there must be a medically viable concept within the belief. He eventually developed the first vaccination to eradicate smallpox: one of the most significant advancements ever made in public health. As stated by the World Health Organization, in May 1796, Jenner used material from a cowpox sore on Sarah Nelmes, a milkmaid, to inoculate James Phipps, an eight-year-old boy.

It was a clue hiding in plain sight

It should be noted here that what made the discovery remarkable was the fact that the clue was right there before everyone else’s eyes all along. Historical articles reviewed and published on PubMed Central show that people living in agricultural communities were already convinced that cowpox conferred immunity against smallpox, and this conviction was based on the idea that milkmaids never contracted the dreaded disease of their time after overcoming the infection by close contact with cowpox. What made Jenner’s discovery unique was his ability to realize the scientific potential of the observed phenomenon.


Based on an article on the subject reviewed by the journal PubMed Central, it should be said that Jenner’s contribution can be considered a product of an accumulation of local wisdom combined with medical research and observations. People already believed in the immunity effect of cowpox, but they had not been able to apply that knowledge to medicine before Jenner.

The experiment that changed medicine

This defining event occurred in May 1796, and, as stated by WHO, Jenner took samples from a cowpox lesion on Sarah Nelmes's hand and then used them to inoculate James Phipps. Afterward, during his exposure to smallpox, Phipps remained immune to the disease, which indicated that being exposed to cowpox led to protection against a much more lethal infection. This observation, initially made in a rural environment, gained experimental support at this point.

CDC gives a somewhat similar explanation to the event in question, stating that Jenner noticed immunity among milkmaids before conducting the inoculation, which was followed by documenting its results. Moreover, the CDC states that Jenner's discovery was eventually published, laying the foundation for further discussion in the medical community. Publication became important because an individual observation by Jenner turned into a claim that other scientists could investigate, refute, and reproduce. In addition, a historical publication in the CDC journal, Emerging Infectious Diseases, described Jenner's observations of milkmaids and farmers who were exposed to cowpox.

From rural observation to public-health tool

Its long-term impacts could be seen only over decades rather than years. According to historical documents at the CDC, the history of smallpox demonstrates how Jenner’s 1796 experiment was linked to subsequent vaccination campaigns and, ultimately, to the successful eradication of smallpox across the globe. As noted by the Edward Jenner Museum, the idea first observed by milkmaids turned out to be just the beginning of a great public health story. In other words, although Jenner could not eradicate the disease himself, his method became the basis for doing so.