Original Article
Vaccine Allergy? Skin Testing and Challenge at a Tertiary Pediatric Hospital in Melbourne, Australia

https://doi.org/10.1016/j.jaip.2019.01.025Get rights and content

Background

The rate of true vaccine allergy is unknown. Children with potential IgE-mediated adverse events following immunization (AEFI) should undergo allergy investigation that may include skin testing or challenge. Previous protocols tend to be highly conservative and often suggest invasive testing for all, a practice not evidence based, technically difficult, and unpleasant in children. It has more recently been suggested that skin testing may be restricted to those with allergic-like events within the first hour and those with a history of anaphylaxis.

Objective

We aimed to describe the outcome of vaccine skin testing and challenge in children referred to a tertiary pediatric hospital with a potential IgE-mediated AEFI. The secondary aim was to identify any significant risk factors for vaccine allergy.

Methods

A retrospective review of all children (<18 years) who underwent vaccine skin testing (skin prick testing or intradermal testing [IDT]) or challenge over a 5-year period (May 1, 2011, to April 30, 2016) at the Royal Children's Hospital Melbourne is presented.

Results

There were 95 admissions in 73 children. Eight percent (6 of 73) of children had confirmed vaccine allergy (positive skin testing or challenge to the index vaccination). Two had positive IDT to a suspect vaccine but challenge negative to an alternative brand vaccine. Two had negative IDT but subsequent positive challenge and two had immediate urticaria on challenge without prior skin testing. All children in the positive group either had index reaction within 15 minutes of vaccination or had history consistent with anaphylaxis.

Conclusions

The vast majority of children (92%) presenting with a potential IgE-mediated AEFI are able to tolerate challenge to a suspect vaccine without reaction. We present our investigation protocol recommending skin testing in all children with anaphylaxis and challenge with a suspect vaccine if negative testing or previous nonanaphylactic potential IgE-mediated AEFI.

Section snippets

Methods

A retrospective review of all children, under the age of 18 years, who underwent in-hospital vaccine skin testing and/or challenge over a 5-year period (from May 1, 2011, to April 30, 2016) is presented. The Royal Children's Hospital is a major tertiary care referral allergy center located in Melbourne, Australia. The study was approved by the Human Research Ethics Committee of the Royal Children's Hospital, Melbourne, Australia (DA013-2017-16).

Study population and vaccines challenged

There were a total of 95 allergy testing episodes in 73 children. Eighteen children had both SPT and IDT. There were 59 children with 73 separate vaccine challenges (without preceding skin testing). Children with IDT to 1 vaccine were also included in the challenge group if they underwent challenge to a separate vaccine without preceding IDT. These results are shown in Figure 1.

The number of each vaccine challenged is demonstrated in Table I. The ages of children included in this study range

Discussion

Potential hypersensitivity AEFI are commonly reported, but the incidence of true vaccine allergy is likely to be much lower, with the rate of anaphylaxis reported to be 0.65 cases per million vaccine doses in children and adolescents10 and vaccine-specific anaphylaxis rates ranging from 0 to 5.14 per million vaccine doses.11 We found a rate of 8% of true vaccine allergy in our cohort; however, it must be noted that this is in patients already deemed suspicious of a previous IgE-mediated vaccine

Conclusions

In conclusion, we find that the vast majority of children presenting with a possible IgE-mediated adverse event after vaccination are tolerant to a suspect vaccine or antigen on rechallenge. We identified that all children with positive testing either had index reaction within the first 15 minutes after vaccination or history consistent with anaphylaxis.

Given our findings, we present our investigation protocol. We hope that this proposed protocol will assist in the appropriate investigation

References (18)

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    Allergic reactions to vaccines are rare, and few studies have reported on evaluations of a large group of patients. Cheung et al101 reported their retrospective experience with evaluating 73 Australian children suspected of having vaccine allergy. Most had immediate reactions, with 69% reporting reactions within 15 minutes.

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No funding was received for this work.

Conflicts of interest: K. P. Perrett is supported by a Melbourne Children's Clinician-Scientist Fellowship and her institution, Murdoch Children's Research Institute, has received research grants from DBV, GlaxoSmithKline, MedImmune, Novartis, Novavax, and Pfizer.

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