Definition of Smallpox vaccine

Smallpox vaccine: A vaccine containing a live virus called vaccinia used to prevent smallpox. The vaccine does not contain the variola virus that causes smallpox. Through the use of the vaccine, smallpox was eliminated from the world in 1977. Routine vaccination against smallpox ended in 1972 The level of immunity among persons who were vaccinated before 1972 is uncertain. In people exposed to smallpox who are not immune to the disease, the vaccine can lessen the severity of or even prevent the illness if given within 4 days of exposure.