Rash was the third most common adverse events reported by the U.S. Vaccine Adverse Event Reporting System (VAERS) during 1991–2001 (occurring in 11% of the reports), following fever, and injection-site reactions . However, rash is a broad term encompassing many different morphologies and causative etiologies. Furthermore, there are multiple definitions for the different morphologies , , , , as well as different skill levels and experience of those reporting these events. While there are previous and ongoing projects attempting to standardize the dermatologic lexicon (http://www.dermatologylexicon.org/), there currently exist no standardized guidelines for recording and analysis of these adverse events following immunization (AEFI) in vaccine safety surveillance systems or vaccine clinical trials.
The Brighton Collaboration Vaccinia Virus Vaccine Adverse Events Working Group was formed in January 2003 to standardize case definitions of adverse events following exposure to vaccinia virus (see respective papers published in this volume of Vaccine). Rashes are among the commonly reported adverse events following smallpox (vaccinia) vaccination, and the need to standardize criteria for assessing and reporting rashes following smallpox vaccination was noted. However, rashes are not unique to smallpox vaccination. In this context, and in the broader context of a need for data comparability as discussed in the overview paper in this volume, establishing standardized criteria for assessing rashes as adverse events following any immunization is important for clinicians administering vaccinations and for scientists collecting, analyzing, and communicating data on AEFI.