Anaphylaxis is an acute hypersensitivity reaction with multi-organ-system involvement that can rapidly progress to a severe life-threatening reaction. It has been difficult to provide a robust clinical definition of anaphylaxis because of the non-specificity of symptoms and variability of presentation. Anaphylaxis can occur to a variety of allergens, and is a rare, but well recognised Adverse Event Following Immunisation (AEFI). Several groups have recently tried to provide a working definition of anaphylaxis. This article reviews these definitions and discusses the challenges for vaccine safety in reliably identifying anaphylaxis as an AEFI.
- adverse event