The vaccinia vaccine is made from a live, attenuated vaccinia virus that is related to the smallpox virus. It was used in the past as a single-dose vaccine to protect against smallpox. In the United States, most adults over the age of forty still bear the one centimeter-round scar on their upper arm that was left after receiving this vaccine as a child, due to the unusual way the vaccine was administered.
However, because of the successful eradication of smallpox from the world, the vaccinia vaccine has not been routinely given in the United States since 1972. It is now only used by laboratory researchers working with the vaccinia virus. Since the terrorist attacks of 2001, the United States government has prepared a smallpox response plan, which includes manufacturing enough vaccinia vaccine to vaccinate every person in the United States.