Smallpox - Atopic Dermatitis and Smallpox Vaccination

by Jon M. Hanifin, MD

People with atopic dermatitis (AD) tend to have a mild immune defect in their skin that occasionally allows certain viruses such as herpes simplex, warts, molluscum contagiosum and vaccinia (the live virus used for immunizing against smallpox) to spread over the skin. The spreading vaccinia infection is called eczema vaccinatum. While the other viruses generally are not a significant problem, vaccinia can also spread internally and sometimes cause a lethal infection. Vaccinia can also infect broken and disrupted skin such as burns and certain diseases, including eczemas other than AD; for example, contact dermatitis (e.g. poison ivy), nummular eczema, etc. It appears the risk to those patients resolves when they heal. AD may carry a lifetime risk since, in past vaccination programs, even people with normal skin but a history of eczema in childhood sometimes developed eczema vaccinatum.

The threat of smallpox as a weapon of bioterrorism has forced governments to consider vaccination as a preventive measure. This logical proposal is counterbalanced by the likelihood that a small proportion of those immunized will get vaccinia infections and some may die. The size of this risk is difficult to estimate because of many factors. Routine vaccination was discontinued in 1972 so we have only historical information and sketchy records. AD was imprecisely diagnosed in those days so the incidence of problems is uncertain. The frequency of AD in the population appears to have tripled in the past forty years, hence many more people may be at risk. The prevalence of AD in the population cannot be precisely known. Our studies estimate that 5-10% of Americans have had childhood AD and that, by adulthood, about 40% of those have no residuals. For all types of eczema, a national survey suggested that 11% were affected.

Government agencies such as the CDC are working hard to reduce risk by developing detailed questionnaires that will identify people with AD, or close contacts with AD, to keep them from being exposed to the vaccinia virus. There are currently no cases of smallpox in the world so we need to take every precaution not to endanger people with AD in whom the prevention might be more dangerous than the disease. At the present time, vaccination planning is directed at only military personnel, emergency responders such as police and firefighters, and approximately 500,000 first-line health care workers. Currently there is no declared intent to vaccinate the general population unless there is a wide-scale introduction of smallpox.