Safe Administration of Flu Vaccine to Egg Allergic Children

Overview

Historically, providing influenza vaccination of egg allergic children and young adults (EAC) with a history of anaphylaxis to egg, or other severe symptoms of an allergic reaction to egg (e.g., severe hives, swelling, or asthma), has been contra-indicated, though vaccination of children with less severe egg allergy has been shown to be safe. Though many children with severe egg allergy, including anaphylaxis, have received past influenza vaccination anecdotally, very few data exist to show this procedure is safe. The investigators propose a double blind, placebo-controlled randomized, prospective multi-centered study to a) demonstrate seasonal trivalent influenza vaccine (TIV) can be safely given in a single dose (as opposed to through 2-step graded dosing of 10% then 90% of the vaccine dose) to EAC despite history of anaphylaxis or previous severe allergic reaction to egg; and b) provide further evidence that adverse outcomes are not related to ovalbumin (egg) content in TIV. Study participants must have a documented history of a severe egg allergy, substantiated by both a history of clinical reactivity AND either a positive skin test or ImmunoCAP/RAST test greater than 0.7 kUA/L. Participants will be randomized to receive either a 2-step graded challenge or a single dose given after a small placebo dose of saline (to mimic the graded challenge). If required, all participants will receive a booster vaccination as a single dose.

Seasonal Trivalent Influenza Vaccine (TIV) is grown in embryonated chicken eggs, and since it contains residual egg protein (ovalbumin), providing TIV to egg allergic children (EAC) could potentially provoke allergic reactivity. Because of this possibility, historically caution has been advised in providing TIV to these children, and the vaccine has been withheld in certain individuals, though for many it has been safely administered after vaccine skin testing and stepwise administration. In the 2009 American Academy of Pediatrics Red Book (and previous editions), a history of severe allergic reactivity to egg is a contraindication to receiving TIV, though it is acknowledged that less severely egg allergic kids have safely received TIV if precautions had been taken. In the past year, several studies have emerged that demonstrate that most, if not all, EAC can safely be vaccinated with both TIV ad the H1N1 vaccine. A recent 5 year review of TIV administration in EAC ages 6 mo-36 mo, showed safe administration to 135 EAC after TIV skin testing, including 14 subjects with a history of anaphylaxis to egg. Another large, retrospective study of non-anaphylactic EAC showed TIV could be successfully administered using a 2-step protocol without skin testing to TIV. In a single center H1N1 vaccine study last fall, 105 EAC received either a full vaccine dose if skin tests were negative, or a 2-step graded challenge if the tests were positive, including 25 subjects with a history of anaphylaxis. No allergic reactions resulted, regardless of the results of skin testing, the method of administration, ovalbumin content of the vaccine, or use of a different booster lot without pre-testing. In a sister-study, 68 H1N1 participants prospectively received TIV safely without graded challenge, including 13 EAC with a history of egg anaphylaxis. A large prospective, Canadian multi-centered study, using an adjuvanted H1N1 preparation containing 0.03μg/mL of ovalbumin, was safely given to 72 individuals with either a history of severe cardiopulmonary reactivity to egg or a history of poorly controlled asthma (this group was not further broken down), via 2-step graded challenge. Thus, these studies suggest it is safe for EAC with a history of anaphylaxis to receive TIV and H1N1 without pre-testing, suggest that use of a 2-step graded challenge may be unnecessary, and show some evidence that past egg allergy severity may not be an important factor in vaccine tolerance. Recent guidelines published by the AAAAI suggest a flexible approach is reasonable, and that EAC can receive TIV without prior skin testing through either a single dose or a 2-step approach. This double blind, randomized, placebo-controlled, multi-centered study aims to investigate the safety of TIV given to EAC with a history of a severe past reaction or anaphylaxis to egg, and aims to show that a single dose route of administration is safe and sufficient. Participants with new or established severe egg allergy (see eligibility criteria) will be randomized to receive either a 2-step (10%, followed by 30 min. observation, then residual 90%) graded challenge or a single dose of TIV given 30 minutes after a placebo dose of normal saline is administered (to approximate the graded challenge). Vaccine tolerance will be analyzed and compared to ovalbumin content of the vaccine lots, as well as to baseline characteristics of the participant's egg allergy and allergic history. Secondary outcomes originally posted on the www.clinicaltrials.gov website were hypotheses which were aims of complex data analysis but were not in and of themselves actual outcome measures. Therefore these have been deleted from the record