Flu vaccine and egg allergy

November 24, 2010

Some people have allergies to chicken eggs, usually to the protein in the egg white called ovalbumin.

Current influenza vaccines are made in chicken eggs because the virus grows in them and eggs are somewht readily available. Vaccine manufacturers kill the virus and extract the virus proteins from the eggs, but a very small amount of egg ovalbumin sometimes contaminates the vaccine after it is purified.

For many years, we wondered if the small amount of egg protein in some influenza vaccines would cause a reaction in people who were allergic to eggs. There were no good studies done on this question. Many people with reported egg allergies have taken flu vaccines for years with no problems.

The drug manufacturers did not want to take any risk for such reactions, so they have always said that people with hypersensitivity to eggs should not take the influenza vaccine. That might have been a safe thing for drug manufacturers to do, but it has not been proven, and it leaves many people unprotected who may need the vaccine.

A study recently published in the Journal of Allergy and Clinical Immunology and a position paper from the American Academy of Allergy Asthma and Immunology clarify this question. Egg allergy does not pose any risk to the patient for giving the current influenza vaccines. The amount of ovalbumin in curent vaccines is extremely low; lower than the level needed to cause a reaction.

The products and guidelines for this year’s influenza vaccine and immunization programs have been produced, most of the vaccine has already been given, and things probably will not change this year. I look for the FDA and the drug manufacturers to soften their language for egg allergy next year as these new data become known.

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