Investigation of suspected vaccine allergy
Published online: January 22, 2019
The rate of true vaccine allergy is unknown but concerns about previous suspected Adverse Events Following Immunization (AEFI) can be a barrier for further vaccination. All children with suspected IgE-mediated AEFI should undergo allergy investigation, which may include skin prick testing (SPT), intradermal testing (IDT) or vaccine challenge. However, previous protocols for investigation tend to be highly conservative and often suggest invasive testing for all, a practice which is not evidence based and may be technically difficult and unpleasant in children.
In an article recently published in The Journal of Allergy and Clinical Immunology: In Practice, Cheung et al describe a retrospective review of 73 children who underwent skin testing and/or challenge due to suspected hypersensitivity reaction to a vaccine between 1st May, 2011 to 30th April, 2016. There was a total of 95 testing episodes including 22 testing episodes (18 children) who underwent skin testing.
Only 6 (8%) children had confirmed vaccine allergy (either positive skin test or challenge to suspect vaccination). Two children had positive IDT to a suspect vaccine with subsequent negative challenge to an alternative vaccine and two children had a positive challenge after negative skin testing. There were also two children with positive challenge without prior skin testing, however, these reactions were mild with only cutaneous reaction. We found that all children with positive challenge or skin testing either had an index reaction within 15 minutes of vaccination or had an index reaction consistent with anaphylaxis.
The results of this review highlight that the majority (92%) of children with a potential IgE-mediated AEFI are able to tolerate challenge to a suspect vaccine without reaction. Based on these findings, the authors developed a protocol for investigation of suspected vaccine allergy. They suggest that all children with an index vaccine reaction history of anaphylaxis undergo skin testing while children with an immediate but non-anaphylactic history may undergo observed in-hospital challenge without preceding skin testing.
The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.