There is extensive data regarding the overall safety of the vaccinia virus, which was generated during its use in the eradication of smallpox. The complications associated with vaccinia virus include encephalitis, vaccinia necrosum, and eczema vaccinatum. These complications are more prevalent in immunocomprimised individuals and infants (see Fig. 2) (34-36).
Vaccinia associated encephalitis results from infection of the central nervous system (CNS). Studies have shown viral recovery from the CNS of patients suffering from vaccinia associated encephalitis (35). This dreaded complication can be avoided by use of a tumor selective vaccinia virus.
Vaccinia necrosum is a progressive necrotic ulcer caused by the vaccinia virus. It is more common in immunosuppressed patients and can destroy significant amounts of
tissue producing significant morbidity. The extensive tissue loss may require reconstruction with tissue grafts and can sometimes require amputation. Surprisingly, this dramatic local infection does not cause a systemic viral spread.
Eczema vaccinatum originates from the infection of eczematous skin throughout the body by vaccinia. It causes a large viral load that induces viremia with fever and malaise and can sometimes progress to death. Although rare, the side effects of vaccinia virus have been the focus of multiple laboratory experiments and animal models suggest a role of inflammatory cytokines in the pathogenicity of viral infection.
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