Clinical Approach Used in Medical Consultations for Allergic-Like Events Following Immunization: Case Series Report in Relation to Practice Guidelines.

BACKGROUND The Joint Task Force on Practice Parameters (JTFPP) guidelines for the investigation and reimmunization of patients who experienced allergic-like events (ALEs) after immunization are predicated on the likelihood of anaphylaxis, assessed through the time to symptom onset (≤ or >4 hours) and number of systems involved. OBJECTIVE The objectives of this study were to compare the management of a series of patients with ALE in actual practice relative to JTFPP guidelines and to discuss key concepts and considerations in their use. METHODS This retrospective study was based on a chart review of patients who consulted for suspected vaccine-associated ALEs at a large allergy department in Canada. RESULTS Only 3 of the 135 patients who presented ALEs after immunization were referred for suspected anaphylaxis. There was no significant difference in the frequency of skin testing or reimmunization of patients whatever the time to symptom onset or number of systems involved in the ALE. Eight patients whose initial ALE occurred within 1 hour after immunization had a recurrence on reimmunization. Another patient whose initial ALE occurred 10 hours after influenza immunization had throat tightening and difficulty swallowing without objective signs. CONCLUSIONS Most ALEs after immunization are not suggestive of anaphylaxis and should not be managed as such. The definition of anaphylaxis in the JTFPP guidelines is nonspecific and may need to be revisited. Restricting skin testing and graded dose reimmunization to patients whose ALE onset is ≤1 hour (compatible with IgE-mediated reaction) and to those meeting specific clinical criteria for anaphylaxis (whatever the timing) is likely a sufficiently sensitive and cautious approach.