Smallpox, vaccination and adverse reactions to smallpox vaccine

Public fear of the reintroduction of smallpox as a biological weapon or agent of bioterrorism has led to a renaissance of interest in smallpox, and a military and public health vaccination programme in the USA. Clinical experience from the last century together with novel immunobiological findings is the basis for current knowledge on smallpox as a disease. Pre-existing knowledge on smallpox vaccination, plus recent vaccination campaign-derived data, is the basis of current risk-benefit assessments. This article summarizes, from a dermatologist's point of view, current aspects of smallpox, smallpox vaccination and adverse reactions to vaccinia, the live virus smallpox vaccine.

The smallpox vaccination campaign in the USA has involved over 600,000 vaccinees, and has largely confirmed incidence data on complications. An increased rate of myopericarditis is the new finding in the current vaccination campaign. Immunodeficiencies, manifest atopic dermatitis lesions and a history of atopic dermatitis remain contraindications to vaccination. Plasmacytoid dendritic cells are a key regulator of the human antiviral immune response and are recruited to inflamed skin in many skin diseases, but are depleted in atopic dermatitis lesions. The lack of plasmacytoid dendritic cell recruitment, together with the missing upregulation of antiviral peptides such as cathelicidin LL37 in atopic dermatitis lesions, is considered relevant for an atopic dermatitis patient's susceptibility to eczema vaccinatum.

Recent experience from the US smallpox vaccination campaign has largely confirmed what was known in the 1960s. Current immunobiological research will enhance our understanding of the interaction between poxviruses and the skin's immune system.