The vaccinia virus is a member of the Poxviridae family and is best known as the virus used in the smallpox vaccine. It is a large, double-stranded DNA virus that can infect various animals and humans. Vaccinia virus is not known to cause severe disease in healthy individuals, making it a suitable candidate for vaccination. This virus plays a crucial role in the eradication of smallpox, a deadly disease that affected millions before its global eradication in 1980. The use of the vaccinia virus in vaccines has helped to provide immunity against smallpox, contributing to public health efforts worldwide.