Reactions of Norwegian children with severe egg allergy to an egg-containing influenza A (H1N1) vaccine: a retrospective audit

Design Retrospective audit. Setting Secondary paediatric outpatient clinic, Tromsø, Norway. Participants The participants were 80 (62.5% boys and 37.5% girls) children and adolescents with a diagnosed egg allergy who had to be on an egg-free diet and be unable to eat any food containing any amount of egg, including egg-containing baked goods, without an allergic reaction to egg protein. We also included patients who were sensitised to egg but had never been exposed to egg or egg-containing baked goods and were on an egg-free diet. Other atopic diseases among the study participants were also registered. Intervention The vaccination took place from November to December 2009. The patients were vaccinated with a monovalent influenza A (H1N1) vaccine that had an ovalbumin content <0.33 μg/ml. They were divided into two groups, receiving the vaccine either as a single dose or as a fractionated dose. Patients were selected for the fractionated dose because of their prior reaction to egg or because they never had been exposed to egg. Primary outcome There were no serious adverse reactions to the vaccine; only one mild adverse reaction and two possible adverse reactions. Results Patients ranged in age from 10 months to 16.5 years. Thirty-eight (48%) patients received a fractionated dose. Sixty-three (79%) had one or more atopic disease apart from egg allergy. With regard to atopy, serum specific IgE levels or skin prick test, there were no significant differences between the groups receiving the vaccine as a fractionated or as a single dose. Conclusions The study confirmed that patients allergic to egg can be safely vaccinated with a regular influenza vaccine containing <0.333 μg/ml ovalbumin, even if these patients had displayed previous anaphylactic reactions to egg and had been diagnosed with concurrent atopic diseases.