When was the first vaccination campaign carried out?

The first vaccination campaign is usually traced to the late 1790s, when Edward Jenner developed the smallpox vaccine in 1796. Jenner observed that milkmaids who had caught cowpox seemed protected from smallpox, a far deadlier disease. He tested this idea with a boy named James Phipps and later showed that exposure to smallpox no longer made the child ill. Jenner’s work led to organized vaccination efforts and eventually to the global eradication of smallpox, certified by the WHO in 1980.