Egg allergy is the second most common food allergy, affecting 1 percent to 2 percent of all children. In the United States, this corresponds to between 150,000 to 250,000 influenza-vaccine-eligible preschoolers. Anne Des Roches and coworkers at the Institutes of Health Research in Canada recently examined whether egg proteins contained in the influenza vaccine posed a real or only theoretical risk to patients with severe egg allergy (Des Roches A, et al., “Egg Allergic Patients Can Be Safely Vaccinated Against Influenza,” J Allergy Clin Immunol. 2012 Nov;130(5):1213-1216.
To answer this question, the authors conducted a prospective cohort study recruiting and vaccinating patients with egg allergy, including severe egg allergy (i.e., those with anaphylaxis or cardiorespiratory symptoms following egg ingestion). Patients were examined immediately before vaccination and remained under observation for 60 minutes post-vaccination. Over a span of five influenza seasons, 457 doses of trivalent inactivated influenza vaccine were administered to 367 patients among whom 132 had a history of severe egg allergy. None of the 367 patients developed anaphylaxis. The quantity of ovalbumin contained in these influenza vaccines ranged from 0.06 ug to 0.31 ug per dose (in other words, as much as 310 billionths of a gram of ovalbumin).
The authors also reviewed the medical literature, identifying an additional 4,172 egg-allergic patients in 26 studies who had safely received influenza vaccine (513 of those patients had severe egg allergies). The authors concluded that the quantity of egg protein contained in influenza vaccines is not sufficient to induce an anaphylactic response in patients known to have severe egg allergies, writing, “The risk of anaphylaxis appears sufficiently low for patients with egg allergy to be vaccinated like all other individuals without requiring administration by an allergist.”