Late in the 17th century, 17 - year - old Molly Walsh, an English dairymaid accidentally spilled a bucket of milk and stood trial for stealing it. (educationworld.com)
The English physician knew that dairymaids who contracted cowpox, a comparatively mild skin disease, became immune to the much deadlier smallpox, which at the time killed 400,000 Europeans a year. (discovermagazine.com)
If you work on vaccines you know the story of British physician Edward Jenner, whose observation that dairymaids infected with cowpox made them resistant to the far more virulent smallpox virus led him to develop, in 1796, the first experimental vaccine. (iavireport.org)