 CDC Home   Vaccine Overview  The Smallpox Vaccine  The smallpox
vaccine helps the body develop immunity to smallpox. The vaccine
is made from a virus called vaccinia which is a “pox”-type virus
related to smallpox. The smallpox vaccine contains the “live”
vaccinia virus—not dead virus like many other vaccines. For that
reason, the vaccination site must be cared for carefully to
prevent the virus from spreading. Also, the vaccine can have
side effects (see the section “Smallpox Vaccine Safety” in this
fact sheet). The vaccine does not contain the smallpox virus and
cannot give you smallpox.   Length of Protection   Receiving the
Vaccine    Smallpox vaccination site Days 4 through 21  view
enlarged image  Post-Vaccination Care  After vaccination, it is
important to follow care instructions for the site of the
vaccine. Because the virus is live, it can spread to other parts
of the body, or to other people. The vaccinia virus (the live
virus in the smallpox vaccine) may cause rash, fever, and head
and body aches