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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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