By Luciana Borio, M.D., March 27, 2007
Last week, Reuters reported  that a 28 month old child developed eczema vaccinatum after contact with his father, a soldier who had been vaccinated with the smallpox vaccine in preparation for deployment to Iraq. The toddler was admitted to the hospital on March 3, and became critically ill. A physician involved in his care described the rash as involving “80 percent of the child’s body.” The child was initially treated with vaccinia immune globulin and a dose of cidofovir; however, his condition continued to worsen. An antiviral drug candidate, ST-246, which is under development by Siga Technologies, was administered under an IND protocol, resulting in clinical improvement.
In theory, there are three conditions that may result from contact with a person recently vaccinated with the smallpox vaccine :
Vaccinia necrosum (progressive vaccinia): A necrotic lesion at the site of vaccination that enlarges, may be associated with metastatic necrotic lesions elsewhere in the body, and typically occurs in a person who has an underlying immunodeficiency.
Eczema vaccinatum: Vaccinial lesions that may be isolated or generalized, and occur at places other than the vaccination site, typically in a person with a history of or active atopic dermatitis or eczema.
Accidental infection: Vaccinial lesions resulting from the accidental implantation of vaccinia virus in a healthy individual. While these lesions may occur in any part of the body, they are most serious if implanted in the eye as it may lead to vaccinia keratitis, which is potentially threatening to the eyesight.
In 1963 and 1968 the CDC conducted 2 national and 2 state surveys to assess the incidence of complications from smallpox vaccination [4-7]. The frequencies of eczema vaccinatum acquired by contact ranged from 8.7 to 10.7 cases per million primary vaccinees in the national surveys, and 16.8 to 20 cases per million primary vaccinees in the state surveys. The surveys indicated that “virtually all of those from whom vaccinia virus was transferred were primary vaccinees” . A small proportion had no active lesions of atopic dermatitis at the time of exposure to vaccinia. A separate analysis showed that all of the deaths attributed to eczema vaccinatum between 1959 and 1968 occurred in contacts . Most cases of contact eczema vaccinatum occurred in children, and in virtually all cases as a result of family contact or contact with close playmates, and not from casual contacts in the community. Curiously, no cases of vaccinia necrosum were acquired by contact.
This recent unfortunate event represents the first report of eczema vaccinatum since smallpox vaccination resumed in 2002. Although the civilian smallpox vaccination program has come to a halt, the Department of Defense continues to immunize at-risk personnel. The prevalence of atopic dermatitis in the U.S. has significantly increased since the 1960s, and most of those vaccinated today are primary vaccinees. Thus, it is critically important for vigilance to remain high so that preventable adverse effects are indeed prevented.
Steenhuysen J. Toddler improving on experimental smallpox drug. Reuters Mar 20, 2007, 9:21AM EDT. (Accessed October March 26, 2007, at http://www.reuters.com/article/healthNews/idUSN1953739120070320)
Toner E, Borio L. CBN Report: Smallpox Antiviral Effective in Animal Trials. October 23, 2006. (Accessed March 26, 2007, at http://www.upmc-cbn.org/report_archive/2006/10_October_2006/cbnreport_102306.html.)
Lane JM, Ruben FL, Abrutyn E, Millar JD. Deaths attributable to smallpox vaccination, 1959 to 1966, and 1968. JAMA 1970;212:441-4.
Vaccine reaction images, from the CDC: https://www.cdc.gov/smallpox/clinicians/vaccine-adverse-reaction-images.html
Smallpox vaccination and adverse events training module, from the CDC