Following
primary vaccination, high titers of vaccinia virus are
extruded onto the surface of the site. After revaccination,
less virus is present on the skin. This surface virus
is easily transferred to the hands and to fomites. Either
may be the source of inoculation elsewhere, but most
implantations occur as a result of transfer from hand
to skin or to mucosa.
The vaccination site is pruritic and many vaccinees,
particularly children, tend to scratch or otherwise
contact the site. Virus is then transferred to normal
skin by touch or scratch. Minor breaks in the skin provide
a fertile field for implantation. Virus is more easily
transferred to abnormal skin or mucosa. Since the virus
is highly dermatotrophic a primary vaccination reaction
occurs at the site of implantation.
In normal individuals, each lesion will follow the same
course as the primary vaccination. If the individual
has a cell-mediated immune defect, however, the implantation
can be serious and life threatening. Please see the
Progressive
Vaccinia page for detailed information.
Lesions in eczematous skin, in disrupted skin and in
the eye pose special hazards, as the infection can be
extensive in skin lesions and a threat to eyesight in
the eye.
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