Need for developing case definitions and guidelines for adverse events following exposure to vaccinia virus:
Following a declaration by The World Health Assembly in 1980 on the worldwide eradication of smallpox , comprehensive smallpox vaccination programs around the world were stopped. Today, >50% of the world’s population is potentially unprotected against smallpox disease . Recent warnings about the possible threat of using smallpox virus as a biologic weapon ,  prompted a resurgence of public health vaccination programs against smallpox.
In this context, and in the broader context of a need for data comparability, as discussed in the overview paper in this volume, establishing criteria for assessing adverse events following smallpox (vaccinia) vaccination is important for clinicians administering the smallpox vaccine and appropriately treating patients with adverse events following immunization (AEFI), and also for scientists collecting, analyzing, and communicating data on AEFI. Understanding the normal changes and progression of a successful vaccine take is crucial for early recognition of complications. Frey et al. ,  completed two double-blind studies, using different dilutions of smallpox vaccine in previously unimmunized adults, and  noted the following descriptions about the vaccination sites (p. 1266):
“Success was defined by the presence of a primary vesicle at the inoculation site seven to nine days after scarification. Other signs and symptoms of the replication of vaccinia virus include edema, tenderness, and erythema at the site of vaccination and regional lymphadenopathy. Subsequently, the vesicle evolves into a small ulcer over which a scab forms [2nd week post vaccination], ultimately leaving a small scar [3rd week post vaccination]”.
Successful vaccination correlates with the laboratory demonstration of the development of a cytotoxic T-cell response, lymphocyte proliferation, neutralizing antibodies, and vaccinia virus-specific interferon-γ production. This combination of clinical and laboratory response to smallpox vaccination provides long-term, and perhaps life-long immunity .
This paper lists, in Sections 2 Case definition for PV, 3 Guidelines for data collection, analysis, and presentation of PV as an adverse event following immunization, respectively, the case definition and guidelines for data collection, analysis, and presentation that the Brighton Collaboration Vaccinia Virus Adverse Events Working Group has developed for the standardized collection and assessment of progressive vaccinia (PV) following exposure to vaccinia virus, with applicability in study settings with different availability of resources and access to health care. Widespread use of this definition with its guidelines will enable data comparability and lead to a better understanding of the adverse event.
1.2. Methods for the development of the case definition and guidelines for PV following exposure to vaccinia virus
Following the process described in the overview paper in this volume , a Brighton Collaboration Vaccinia Virus Vaccine Adverse Events Working Group was formed in January 2003 with 32 members. Members volunteered for at least one of five different subgroups for one adverse event following exposure to vaccinia virus The PV subgroup included 10 members with a clinical or public health background. The member composition and results of the web-based survey completed by the reference group (discussed in the overview paper in this volume) with subsequent discussions in the working group can be viewed at: http://brightoncollaboration.org/internet/en/index/working_groups.html.