Egg sensitivity and flu shot: doctors' dilemma

"On the one hand we are concerned about the devastating effects of the new strain of flu, and on the other we aren't sure if a history of eggs sensitivity is enough to hold the shot or spray," said Bobby Q. Lanier, M.D., clinical professor of paediatrics at the University of North Texas HSC in Fort Worth, Texas, and executive medical director of the American College of Allergy, Asthma and Immunology (ACAAI).

The process of using fertilized chicken eggs to grow the virus associated with influenza was a medical breakthrough in 1931, Dr. Lanier said. Before that discovery, the only treatment for flu was to transfuse blood from a survivor of flu to one with the symptoms. The egg technology opened up vaccines to literally billions of people.

Historical issues

While the vaccine production now removes virtually every trace of chicken protein, there were historical issues of vaccines causing major allergic reaction because of retained egg protein. Amal Assa'ad, M.D., professor at Cincinnati Children's Hospital Medical Centre in Cincinnati, Ohio, and vice chair of the ACAAI Adverse Reactions Foods Committee, will be presenting a novel way to classify children (and adults) as to their risks at the ACAAI Annual Meeting in Miami Beach, Fla.

"Some allergic patients are at greater risk of a reaction to the 2009 vaccines, both H1N1 and the usual respiratory viruses in the normal flu shot and mist. This high risk group includes patients with a history of a positive skin test or an elevated blood test to egg, who have had allergic reactions to eating egg, or who had a reaction to flu vaccination in the past," Dr. Assa'ad said.

Dr. Ass'ad has classified possible reactors in five colour-coded groups and makes these suggestions:

• Blue Group - Minimal Risk. Patients with a history of skin test or serum IgE positivity or clinical reaction to either egg or previous flu vaccines - who can eat whole eggs safely without allergic reaction - should receive either the inactivated (IM) or live (intranasal) vaccine at their general paediatrician's office. This should comprise the vast majority of patients this year.
• Green Group - Low Risk. Children who have had recent (less than 2 years) skin test or serum IgE positivity to egg, but who do not react to ingestion of baked products containing egg, should receive the inactivated flu vaccine at full-strength (or graded challenge in special cases) at their general paediatrician's office or the allergy clinic. Adrenalin should be available.
• Yellow Group - Moderate Risk. Any patient avoiding eggs entirely for any medical reason should be evaluated by an allergist. Patients who have had recent skin test or serum IgE positivity to egg who do react to baked products containing egg, or who have a history of allergic reaction to inactivated flu vaccine, should also be evaluated by an allergist. In order to provide the vaccine safely to these patients, we recommend skin testing with the full-strength inactivated flu vaccine and egg extract prior to vaccine administration. If the skin tests are negative, we recommend that the rest of the vaccine be given at full-strength or as a graded challenge. If the vaccine skin test is positive, we would either desensitize the patient to the vaccine and administer it or give chemoprophylaxis in special cases with a flu medication daily for the entire flu season.
• Red Group - High Risk. Patients who have a history of an anaphylactic reaction to egg ingestion or flu vaccination should be evaluated by an allergist. Even patients who have then gone on to tolerate the vaccine later in life should be evaluated by an allergist, as there is significant year-to-year and lot-to-lot variability in the egg protein concentration in the flu vaccine. We recommend that these patients be skin tested to egg and full-strength inactivated flu vaccine prior to administration. Patients with negative skin tests to the vaccine would receive a graded flu vaccine challenge, while patients with positive skin test to the vaccine would receive either desensitization or neuraminidase inhibitor prophylaxis for the entire flu season.
• Grey Group - Special Risks. Patients with immunodeficiency or other contraindications to either of the flu vaccines should be evaluated by an allergist or infectious disease specialist, and their close contacts and caregivers should strongly consider inactivated (i.e. not live) influenza vaccination. Most patients in this group may safely receive the inactivated flu vaccine as a single injection, provided they do not have a history of skin test positivity, serum IgE positivity, or clinical reaction to either egg or prior flu vaccines. Should a patient with immunodeficiency have such an issue, we would treat them similarly to whichever Green, Yellow or Red Group they would otherwise be in, with the general caveat that we do not recommend live vaccine use in this patient population or in pregnant women.

"It is the consensus of most allergists that flu shots can be given to virtually every patient who needs them if the proper procedure is followed," Dr. Lanier said.

Source: University of North Texas HSC in Fort Worth