Vaccinia is a virus that belongs to the Poxviridae family. It is best known as the vaccine used to eradicate smallpox, a highly contagious and deadly disease. The virus is related to the cowpox virus and was historically used in vaccination to provide immunity against smallpox. Vaccinia is not typically associated with disease in healthy individuals, but it can cause mild skin reactions at the vaccination site. In rare cases, it may lead to more serious complications, especially in people with weakened immune systems. Overall, Vaccinia played a crucial role in the global effort to eliminate smallpox.