"The current CDC guidelines in the setting of a smallpox outbreak include a recommendation to immunize anyone with contact regardless of risk factor for an adverse event," lead author Renata J.M. Engler, MD, FAAAAI, from the Walter Reed Army Medical Center in Washington, DC, says in a news release. "Many expert groups are reviewing these questions and considering the fine points of risk-benefit and what other options exist to protect those patients who are at very high risk for serious or even life-threatening smallpox vaccine complications."

Groups especially vulnerable to adverse effects from vaccinia include patients with congenital or acquired immune deficiency diseases such as AIDS, those receiving immunosuppressive therapy for organ transplantation or other conditions, those with active or quiescent atopic dermatitis, and potentially those with similar skin conditions affecting the epidermis.

In individuals with current or prior history of atopic dermatitis, eczema vaccinatum can complicate smallpox vaccination or can develop indirectly through exposure to someone who has recently been vaccinated. After spreading unchecked throughout the skin, the vaccinia virus can cause scarring, blindness, and even death. Vaccinia immune globulin can mitigate or reverse these complications if given sufficiently early.

Current CDC guidelines recommend withholding routine smallpox vaccine from individuals with a current or past history of atopic dermatitis. Nearly half of the population in developed countries, where rates of atopic dermatitis have increased two- to three-fold since the days of routine smallpox vaccination, could therefore be ineligible, as could up to 15% of the U.S. population. Routine mass smallpox vaccination could therefore be problematic, although vaccination in some patients with atopic dermatitis may be justified if the risk of smallpox infection is high, such as after a bioterrorism attack.

The authors call for additional research on the immune response to vaccinia to clarify why atopic dermatitis predisposes to eczema vaccinatum and to develop preventive strategies.

"The very real dangers associated with the live vaccinia virus vaccine may take on a greater urgency today than decades ago given the current numbers of people with pre-existing medical conditions that put them at risk for serious side effects," says co-author Julie Kenner, MD, PhD, from the University of Hawaii in Honolulu. "It is incumbent upon the medical community to protect our population to the best of our ability against these potentially lethal vaccine side effects, while at the same time, protect them from a very deadly disease."

J Allergy Clin Immunol. 2002;110:357-365

Reviewed by Gary D. Vogin, MD

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