The combination of vaccinia and VIG is very rational if post-exposure chemoprophylaxis cannot be given within 7 days of exposure. With the exception of significant immunodeficiency, there are no contraindications to vaccinia following smallpox exposure. Vaccinia immunoglobulin was administered in divided doses at multiple locations over 24 to 36 hours. Patients with HIV infection or other immunodeficiencies would be candidates for VIG alone. Vaccinia cannot be cultured from the vesicles or from the serum of patients with this condition.
Pathogenesis is unknown, but is possibly due to an immunopathologic mechanism.
Usually, this is a self-limited reaction and no therapy is indicated, but VIG may be indicated for severe cases. These included generalized urticarial exanthems, such as erythema multiforme and Stevens-Johnson syndrome. Encephalitis occurs in approximately two individuals per million receiving the vaccine. This complication produced a case fatality rate of 10 to 30 percent and neurologic sequelae in survivors. The pathogenesis is unknown but is probably due to an immunopathologic mechanism because vaccinia cannot be cultured from CSF or brain tissue of patients.