data item adverse event risk difference The AE risk difference depends on both the background incidence of the adverse event (i.e., among nonrecipients) and the relative risk of its occurence in medical intervention recipients versus nonrecipients. Even when the AE rlative risk is high, the AE risk difference will be low if the event is extremely rare. a data item that represents the incidence of the adverse event among recipients of a medical intervention (e.g., vaccinatoin) minus the incidence of the adverse event among otherwise similar nonrecipients. Stratton KR, Howe CJ, Johnson RB. 1994. Adverse events associated with childhood vaccines: Evidence bearing on causality. National Academy Press. Washing, D.C. Page 27. YH