Need for developing a standardized case definition and guidelines for induration at or near injection site as an adverse event following immunization:
Induration and swelling at injection site are commonly reported local reactions following immunization. However, there are no standardized definitions of swelling and induration, and it may be that the term induration is used as synonym for swelling in some reports [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11]. Sometimes, swelling and induration are used interchangeably in the literature, and sometimes both are mentioned, either separately or combined [12], [13], [14], [15], [16], [17], [18], [19], but with no further description of their differences. It is important to develop standardized case definition criteria of induration at injection site in order to systematically distinguish between induration and swelling as well as other local reaction, and ultimately improve global comparability of vaccine safety data on local reactions.
Sections 2 Case definition for induration at or near injection site, 3 Guidelines for data collection, analysis, and presentation of induration at or near injection site of this paper provide the case definition and guidelines for data collection, analysis, and presentation that the Brighton Collaboration Local Reactions Working Group has developed for the standardized collection and assessment of information about induration at or near injection site. Widespread use of this definition with its guidelines will improve data comparability and allow better understanding of the adverse event. The case definition and guidelines are intended to be applicable in diverse geographic, administrative, and cultural regions, regardless of differences in the availability of health care resources.
1.2. Methods for the development of the case definition and guidelines for induration at or near injection site as an adverse event following immunization
Following the process described in the overview paper [20], a Brighton Collaboration Local Reactions Working Group was formed in December 2001 with 12 members with public health, regulatory, clinical and academic, and industry backgrounds. The Working Group identified several injection site reactions to be chosen based on their frequency or severity. It has previously published its case definition with guidelines for nodule at injection site [21]. The Working Group, whose composition is slightly different for each of the definitions depending on availability and interest in a particular topic by Working Group members, has since developed four additional case definitions with guidelines published in this volume. The member composition and results of the web-based surveys completed by the reference group with subsequent discussions in the Working Group can be viewed at: http://brightoncollaboration.org/internet/en/index/working_groups.html.
To guide the decision-making for the case definition and guidelines, a literature search was performed by the Cochrane Collaboration professional search person for local reactions overall including induration in the context of immunization (MEDLINE 1976–2001; search terms included amongst others “induration” or “local reaction” or “inflammation” and “injection site” and “immunization”); the search also included reviews of textbooks and study protocols. Based on a review of the title and abstract of the >970 references identified, we identified more than 120 potentially relevant articles, of which we summarized 26 articles in detail mentioning induration. Structured work on the evaluation or development of a definition for induration at or near the injection site was not found in the literature reviewed. Occasionally, induration was described as a palpable dense swelling or subcutaneous mass [22], [23], [24].
1.3. Rationale for selected decisions about the case definition for induration at or near injection site
This Working Group defined induration as an AEFI as a pathological hardening or thickening of tissue (http://www.cogsci.princeton.edu/cgi-bin/webwn) which corresponds to a clinical diagnosis of a local reaction that is firm to the touch and often has a ‘woody’ feel to it.
