Safe vaccination of patients with egg allergy with an adjuvanted pandemic H1N1 vaccine

Abstract

Background: Because influenza vaccine contains some residual egg protein, there is a theoretic risk of anaphylaxis when vaccinating patients with egg allergy. The objective of this study was to estimate the risk of anaphylaxis in children with egg allergy administered an adjuvanted monovalent 2009 pandemic influenza A/H1N1 influenza vaccine (Arepanrix; GlaxoSmithKline, Mississauga, Ontario, Canada).

Methods: Patients with confirmed egg allergy with a history of respiratory or cardiovascular reactions after egg ingestion were vaccinated in 2 divided doses (10% and 90%) administered at a 30-minute interval, whereas children with other types of egg-induced allergic reactions were vaccinated with a single dose. All patients remained under observation for 60 minutes after vaccination. A 24-hour follow-up telephone call was made to detect any delayed reaction. The main outcome was the occurrence of an anaphylactic reaction according to criteria specified by the Brighton Collaboration.

Results: Among the 830 patients with confirmed egg allergy, only 9% required the vaccine to be administered in divided doses. No patient had an anaphylactic reaction. Nine patients had minor allergic symptoms treated with an antihistamine (1 in the 60 minutes after vaccination and 8 in the following 23 hours), and 3 others received salbutamol (1 in the first 60 minutes after vaccination). Further vaccination of more than 3600 other children with reported egg allergy caused no anaphylaxis based on the criteria of the Brighton Collaboration, although 2 patients received epinephrine for symptoms compatible with allergy.

Conclusion: Although anaphylaxis after influenza immunization is a theoretic risk, vaccination of patients with egg allergy with an adjuvanted monovalent pH1N1 influenza vaccine resulted in no cases of anaphylaxis and on that basis appears safe.