Administration of the Adjuvanted pH1N1 Vaccine in Egg-allergic Children at High Risk for Influenza A/H1N1 Disease

Background In Canada, the pH1N1 influenza vaccine is recommended for children, particularly those less than 5 years of age or with chronic underlying disease. The pH1N1 vaccine, which contains residual allergenic egg white proteins, may pose a risk for vaccination of egg-allergic children. Objective To describe the outcome of pH1N1 influenza vaccine administration to egg-allergic children at risk for severe H1N1 disease. Design/Method Prospective observational cohort study. Children identified as at high risk for egg allergy and H1N1 influenza were vaccinated using a two-dose split protocol in a controlled medical setting. Children were given an initial test dose; if no reaction was noted, the remainder of the dose was administered and the children were followed for allergic reactions. Those who tolerated the split dose and required a second dose of vaccine were offered vaccination four weeks later as one injection. Results Sixty-two egg-allergic children considered at high risk for H1N1 disease received the adjuvanted pH1N1 vaccine. Egg allergy was diagnosed both clinically by an allergist and using skin and/or serum IgE testing. Within one hour of immunization, 2 children developed hives, 1 had a vasovagal response and 1 had a hypo-responsive episode. Fourteen children received the second H1N1 dose and 1 developed erythema and itching. There were no anaphylactic reactions. Conclusion Administration of the adjuvanted pH1N1 vaccine in egg-allergic children at risk for severe H1N1 influenza was safe when performed in a two-dose split protocol in a controlled medical setting.