Date Published: March 2, 2012
Publisher: BioMed Central
Author(s): Julia Elizabeth Mainwaring Upton, David Brian Hummel, Anna Kasprzak, Adelle Roberta Atkinson.
There are numerous, disparate guidelines for influenza vaccination in egg-allergic patients. We aimed to describe the outcome of selectively applied guidelines, based on risk-stratification, to our high risk, egg-allergic, tertiary-care pediatric population.
Egg allergy was confirmed with skin testing. The vaccine administered was an adjuvunated 2009 H1N1 influenza A vaccine with < 0.165 mcg/ml ovalbumin. Patients with mild egg allergy were to receive the vaccination in 1 dose, those with severe egg allergy were to receive 2 split doses, and patients with exquisite egg allergy or significant co-morbidities were to be skin tested with the vaccine (prick full strength, intradermal 1:100 of final concentration without adjuvant) and had 5 step desensitization if the testing was positive, or 1-2 step administration if negative. Patients were observed for 60 minutes after the final dose and anaphylaxis treatment was available. We report the frequency of allergic reactions. Ninety-nine patients were referred and 79 had positive egg testing. Asthma was present in 67% and 30% had prior anaphylaxis to egg. We vaccinated 77 of 79 patients: 71 without performing vaccine skin testing. Two refused vaccination. No patient had a systemic reaction or required treatment. Two patients experienced positive testing to the adjuvanated intradermal vaccine, but were negative without adjuvant. Our results suggest that most egg-allergic tertiary care pediatric patients can be vaccinated with a low ovalbumin content influenza vaccine without prior vaccine testing. Vaccine skin testing, if used at all, can be reserved for special circumstances. The squalene adjuvant may cause an irritant reaction with intradermal testing.
Influenza vaccination has traditionally been contraindicated in individuals with egg allergy [1,2] due to the possibility of an allergic reaction to residual egg proteins. Approaches have been recommended to vaccinate egg-allergic individuals. One approach recommends skin testing prior to vaccination  and use of a graded challenge . However, there has been evidence demonstrating that the influenza skin testing may not be predictive of reactions [5-7] and intradermal testing has been shown to have an irritant response . There is no such data on intradermal skin testing performance with an adjuvanated influenza vaccine.
The study was conducted at The Hospital for Sick Children, Toronto. The protocol was developed in November 2009. Our inclusion criteria were all patients seen in the Egg Allergy-pH1N1 vaccination clinics. The diagnosis of egg allergy was assessed with commercially available egg extract SPT within the last 6 months. This cohort included children that had never eaten eggs. Patients were excluded if their SPT was negative to eggs, or clearly tolerating eating eggs other than in baked products. Specific IgE levels to egg were not assessed.
The egg-allergic patient population we evaluated for vaccination was a tertiary pediatric practice with a high level of anaphylaxis, significant co-morbid conditions, and some with positive flu vaccine tests. Despite this we successfully vaccinated 77 of 79 patients and only skin tested 8/79 patients by using a risk-stratified approach. The only 2 we did not vaccinate were due to patient refusal. No patients had a systemic reaction to vaccination.Some patients received a different administration of vaccine than dictated by their egg allergy alone. There were 13 patients with “mild egg allergy” that were given the vaccine in two graded doses whereas the algorithm suggested a single dose by their egg history alone. Some of these patients had complex medical conditions. For example, one had sickle cell anemia, one had a liver transplant, and one had cerebral palsy and was in a wheelchair. While these conditions are not related to atopy, they may make the recognition and management of a serious allergic reaction more difficult or lessen the parents or physician’s comfort level with risk. Administration of vaccine without prior testing was a change from previous years so the use of the perceived more cautious approach (split dosing rather than single dosing) was not surprising. Three patients that were not tested to the vaccine were given the vaccine in a single dose when two were suggested by our algorithm. Two of these patients had hives and angioedema to egg and one had a combined skin and gastrointestinal reaction. These reactions were determined by the treating physician to be mild and were thus triaged to a single dose. None of these patients had a systemic reaction to the vaccine. The algorithm was only a suggestion and the flexibility for the physician or family to choose a more cautious regimen likely helped compliance.
Our study showed that most egg-allergic, tertiary-care pediatric patients can be safely vaccinated with a low-ovalbumin content influenza vaccine without prior vaccine testing and that vaccine testing and desensitization in egg-allergic patients, if used at all, can be reserved for special circumstances. We only vaccine tested patients deemed to have exquisite egg allergy and/or significant co-morbidity (8 of our 79 patients) and only 2 of our patients had a positive prick test and they still tolerated the vaccine in a graded challenge. We found that the adjuvant likely has an irritant response on intradermal testing. This study adds another 24 patients to the current body of evidence that even patients with a prior history of anaphylaxis to egg can receive an egg-containing influenza vaccine. Based on available evidence, many guidelines now conclude that egg-allergic individuals do not benefit from vaccine skin testing prior to low-ovalbumin content influenza vaccination.
SPT: skin prick test; CSACI: Canadian Society of Allergy and Clinical Immunology; pH1N1: 2009 H1N1 influenza A pandemic.
The authors declare that they have no competing interests.
JU contributed to the conception and design of the protocol, the acquisition of and collection of the data, the data entry, the interpretation of the data and drafted the manuscript. DH contributed to the design of the protocol, the collection of the data, and revision of the manuscript. AK contributed to the design of the protocol, the collection of the data and revision of the manuscript. AA contributed to the conception and design of the protocol, the interpretation of the data and revising the manuscript for important intellectual content. All authors read and gave approval to the final manuscript.