AESI Case Definition Companion Guide: Anaphylaxis Version 2

This document replaces an earlier version of the Anaphylaxis Companion Guide (completed Feb 5, 2021) which accompanied the 2007 Anaphylaxis case definition. A new Working Group was formed in 2021 to review and revise the 2007 Anaphylaxis case definition (Anaphylaxis V-1) due to identified issues of the V-1 definition over-calling events with allergic symptoms as anaphylaxis. The new V-2 case definition was completed in September 2022, and this Companion Guide updates the previous one primarily as regards the tools for data abstraction and application to determine level of certainty. No changes were needed for the other sections including risk factors, background rates and ICD9/10-CM & MedDRA codes. This guide should replace the earlier version and can be used by stakeholders to assess the occurrence of anaphylaxis in several settings including as an adverse event following immunization.