successful use of LLDBs in the United Kingdom such as described abovewas due in part to the adverse event investigated. Viral meningitisis a fairly clearcut diagnosis. The difficulty of addressing issuesabout conditions such as epilepsy, sensorineural deafness, or diabetesfor which the time of onset may be different from the time of diagnosiswas raised. Any condition that is chronic, longterm, or of insidiousonset may be difficult to detect by this method. Unfortunately, theseare the same conditions that are not easily identified in case reports.Fundamental laboratory research, such as the identification of biomarkersfor vaccine-induced pathology, may be required to study conditionsof this sort.

The importance of standardized case definitions was stressed by severalparticipants; to plan ways of finding outcomes reliably, it is necessaryto know with some precision what is being sought. The indicationby a representative of PHS that PHS's case definitions could be madewidely available once they have been determined was well receivedby the participants.

As part of developing the case definitions, attention has been paidto planning search strategies for particular conditions within thedatabase. Given an interest in a particular outcome, it is necessaryto delineate the appropriate combination of possible discharge diagnoses,laboratory data, radiology procedures, pharmaceutical information,and so forth that will be both sensitive and specific in helpingto detect cases of the outcome in question.

A formal system for evaluating LLDBs on a regular basis was suggested.Perhaps this could be done through an oversight panel of three tofive people who could provide an external critique of the study andits methodology. This could be similar to the oversight done forefficacy trials, in which knowledgeable people who are separatedfrom the immediacy of the study review the procedures of a study.

The LLDBs show great, but not unlimited, promise. Unfortunately,they will be unable to detect adverse events of insidious onset orwith a long latency from exposure. Participants urged careful consideration of the adverse events to be studied.