Table 1

Definition of categories of relation of adverse event to study vaccine administration

Relation Definition
Not related The adverse event is obviously explained by another cause and/or the time of occurrence of the adverse event is not reasonably related to the vaccination
Remotely relatedThe adverse event is likely to be explainable by causes other than vaccination
Possibly relatedVaccine administration and the adverse event occurrence are reasonably related in time and the adverse event is explained equally well by causes other than vaccination
Probably relatedVaccine administration and the adverse event are temporally related and the event is more likely to be explained by the vaccine than by other mechanisms
Definitely relatedVaccine administration and the adverse event are temporally related and the adverse event is consistent with the pattern of other known vaccine related events