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Research Strategies for Assessing Adverse Events Associated withVaccines:: A Workshop Summary
Some workshop participants felt that, if case reports are to servea useful function in assessing the safety of vaccines, there is agreat need to improve the analysis of the case reports received inpassive surveillance systems by improving the quality of the informationcontained within an individual case report, by harmonizing the systemsthat collect and analyze the data, and by increasing the proportionof serious events that are reported. The enthusiasm for better utilizingcase reports was not, however, universal. Those with reservationsworried that increasing reporting will merely increase the noiseinherent in the systems and that the resources needed to improvepassive surveillance systems sufficiently would be better spent onother research tools.
Improvements at the level of the individual case report have bothquantitative (more reports and more information in each report) andqualitative (complete, relevant, and necessary information) aspects.A significant factor in the success of passive surveillance systemsis whether the information about the reaction is complete and accurate.This is probably best achieved if a health care professional reportsthe reaction or verifies information received from a nonhealth careprofessional. The problem of underreporting of adverse events associatedwith vaccines is discussed in a subsequent section. Complete informationon the vaccinee and the reaction to a vaccination are important.In addition to information on the patient's history and completedetails of the medical problems with which the patient is presenting,it is important to know about other risk factors (for example, thepossibility that an infectious disease is circulating within thecommunity) that might account for the reaction. As mentioned previously,the absence of an alternative etiologic candidate is one factor insupport of causality. Results of a comprehensive examination areuseful for diagnostic and treatment purposes (What is wrong withthe patient and what treatment should the patient be given?) andfor research purposes (Did the vaccine cause the adverse event? Ifso, what is the mechanism?). A complete workup could be expensive,and it is not clear who should pay for a comprehensive medical examinationof someone experiencing an adverse event after vaccination.
The analysis of adverse events could be greatly improved by harmonizingof the adverse reaction reporting forms, the coding terminologies,and the search strategies used to summarize the information containedin the multiple databases managed by different manufacturers anddifferent countries. In September 1993 FDA sponsored a workshop onharmonization efforts, and the participants were hopeful that theworkshop marked the beginning of more long-term efforts in that direction.Harmonization is an issue for manufacturers (How much effort is madeto obtain complete data? How is the documentation organized? Whatcoding