Egg allergy no bar to flu shot, researchers say

NEW ORLEANS — Most children with egg protein allergies who received influenza vaccinations had no adverse reactions, researchers said at the annual meeting of American Academy of Allergy, Asthma & Immunology, according to MedPage Today.

A retrospective chart review of egg-allergic children receiving at least one flu shot showed that only seven of 135 developed reactions, none systemic, said Laura E. Howe, of the University of Michigan in Ann Arbor.

Even children with a history of anaphylaxis appeared to have no problem with flu vaccines, with no reactions seen in 14 patients, she said.

The seven reactions were mainly hives and/or erythema, with one case of diarrhea and one eczema flare. Two responded to antihistamine treatment and five resolved spontaneously.

"Children with egg allergy can safely receive the seasonal influenza vaccine," Howe concluded.

Almost all influenza vaccines today are cultured in fertilized chicken eggs. Most of the egg protein is removed during the process, but some remains, leading to periodic concerns about their use with egg-allergic patients. Although vaccine cell-culturing techniques that do not involve eggs have been developed, none have been approved in the United States.

Howe added that skin testing for reactions to the vaccine was not helpful, because 10 of 24 patients undergoing either skin-prick or intradermal testing had false-positive results.

Howe reported that 21 percent of egg-sensitive children received the vaccine without prior testing, and suffered no greater rate of reactions than other children.

The results were also confirmed prospectively in a cohort of 50 egg-allergic children vaccinated with the 2009 H1N1 vaccine during the current season, of whom only one had an allergic reaction, also not systemic.

The cohort included 13 with a history of anaphylaxis, none of whom experienced a reaction.

Matthew Greenhawt, a University of Michigan allergist who worked on the prospective study, said there was a simple message for clinicians about flu vaccines in egg-allergic children: "It's safe, period."

He said there was no need to perform skin tests beforehand.

Howe and colleagues reviewed clinic records at the University of Michigan from 2004 to 2009 to identify children with egg allergies who received flu shots.

To qualify as egg-allergic, patients' records had to indicate a history of reactions to egg products, plus a positive result in skin or allergen-specific antibody testing. The age range was 6 months to 3 years.

Of 140 egg-allergic children overall, 135 had received at least one flu vaccination.

Another presentation at the meeting also reported on flu vaccine safety in egg-allergic children, with similar results.

A study of the Fluarix vaccine by researchers at Mount Sinai School of Medicine in New York City found that, of 214 doses administered to egg-allergic children in 2007 to 2009, no anaphylaxis or other serious adverse effects were seen.

There were 13 cases of urticaria or erythema, of which seven were limited to the injection site.

Fluarix contains less egg protein that most vaccines, at less than 1 μg per 0.5 mL, though the product is not currently FDA-approved for children.

Richard Nolan, of Princess Margaret Hospital for Children in Perth, Australia, who was not involved with either study, agreed that flu vaccination generally poses no problem for children with egg allergies.

"So far it looks safe because there is such a small amount of egg protein compared with what usually causes egg allergy," said Nolan, who has conducted similar retrospective analyses at his institution.

The studies, which have not yet been published in peer-reviewed journals, had no external funding.