Vaccinia, the smallpox vaccine, is a very closely related virus. You infect someone with it, they maybe get a bad rash at worst, and then they are immune to man

Vaccinia, the smallpox vaccine, is a very closely related virus. You infect someone with it, they maybe get a bad rash at worst, and then they are immune to many of the poxes. Cowpox can and has been used the same way, too. This is why vaccination is named after cows. Some poxes are awful for the primary host. Camelpox apparently kills about a quarter of camels that contract it. Just like smallpox (humanpox?) kills about 25% of humans, actually. But camelpox rarely even infects humans, and is self-limiting when it does. Monkeypox is bad in humans. Almost as bad as smallpox, but not as contagious.