Anonymous ID: a7d29f Nov. 18, 2021, 11:21 a.m. No.15028635   🗄️.is 🔗kun

https://www.britannica.com/science/cowpox

"The preventive effect of vaccination, or intentional inoculation with the vaccinia virus, was demonstrated by Edward Jenner in 1796, following the observation that milkmaids who had been infected by cowpox during milking subsequently were immune to smallpox."