In what year did Edward Jenner discover that cowpox (vaccinia) protects against smallpox?

Edward Jenner's discovery that cowpox provides immunity against smallpox occurred in 1796. This pivotal moment in medical history marked the inception of vaccination, as Jenner demonstrated that exposure to the relatively mild disease of cowpox could confer protection against the much deadlier smallpox disease. Jenner's work laid the groundwork for future vaccinations, ultimately leading to the eradication of smallpox in 1980. By using cowpox material from the lesions of infected cows and injecting it into individuals, Jenner provided empirical evidence that helped to shape the understanding of immunology and preventive medicine.