No One Knows What’s Inside the Smallpox Vaccine
At the heart of history’s most successful eradication campaign is a mystery. The smallpox vaccine—now also being deployed against monkeypox—contains a live virus that confers immunity against multiple poxviruses. But it is not smallpox or a weakened version thereof. Nor is it monkeypox. Nor is it cowpox, as suggested by the vaccine’s famous origin story involving pus taken from an infected milkmaid to immunize an 8-year-old boy.





























