Medical Definition of Smallpox vaccine

  • Medical Author:
    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

Smallpox vaccine: A vaccine that contains a live virus called vaccinia that is used to prevent smallpox. The vaccine does not contain the variola virus that causes smallpox, but exposes the immune system to proteins that look like the virus so that an immune response occurs. Through the use of the vaccine, smallpox was eliminated from causing human infection in 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.

Reviewed on 12/11/2018

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