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October 09, 2012

Is Flu Shot Safe for Patients With Egg Allergy?

It is the season for flu shots... and with that... we invariably get phone calls from patients asking whether it is safe to receive the flu shot if they are egg allergic. Generally speaking, the blunt answer is that it is safe... even if you have a life-threatening egg allergy.

Why the concern? The flu shot vaccine (both H1N1 and seasonal) are grown inside eggs which is where this concern arises. It also doesn't help that the pre-flu shot questionnaire specifically asks about egg allergy. Though egg-based, during vaccine production the egg protein is filtered out such that there should be no egg contaminants in the final vaccine. However, it is theoretically possible that some egg may still be present in the vaccine.

Given the infinitesimal possibility of egg contaminants, is the concern still legitimate?

There has been a recent study by Canadian researchers who followed 367 egg-allergic people, mostly children, who got the flu shot over five years. Almost one-third of these patients had a significant history of anaphylaxis after eating eggs causing serious symptoms like trouble breathing or a drop in blood pressure. However, in this study, NOT ONE of those patients, experienced a serious reaction to the flu vaccine. Only 13 of the 367 had mild "allergy-like" symptoms, like itchy skin or hives, within a day of the shot.

Furthermore, numerous past studies that involved close to 4,000 egg-allergic people who got the flu shot revealed not a single case of a serious allergic reaction.

However, if such studies still do not alleviate anaphylaxis concern if egg-allergic...

You can either get one of the new completely egg-free flu vaccine Flucelvax or Flublock or...

To play it safe, the absolute safest way for a patient with egg allergy to get the flu shot is via a few steps:

1) Get a test dose of the flu vaccine where a small amount (0.025cc typically) of the flu vaccine is administered sub-dermally.
2) Wait 10-20 minutes.
3) If there's no reaction (redness and swelling of the skin), get the shot properly into the muscle.
4) If there's a large wheal reaction, it's probably best not to get the flu shot or see an allergist to get desensitized prior to receiving the injection.
5) If flu shot given, make patient wait 30 minutes to observe for any adverse reaction.

Not all practices may be familiar with these particular steps. If that's the case, request to take the flu vaccine to an allergy office (including ours), and have us administer it. (Please note that we do not provide egg desensitization.)

If you are only IgG allergic and not IgE allergic to egg, no need to worry. Get the flu shot.

For a more in depth discussion, click here to read a document prepared by the American Academy of Allergy Asthma & Immunology.

Reference:
Egg-allergic patients can be safely vaccinated against influenza. Journal of Allergy and Immunology. In Press. Published Online Oct 1, 2012
Fauquier blog
Fauquier ENT

Dr. Christopher Chang is a private practice otolaryngology, head & neck surgeon specializing in the treatment of problems related to the ear, nose, and throat. Located in Warrenton, VA about 45 minutes west of Washington DC, he also provides inhalant allergy testing/treatment, hearing tests, and dispenses hearing aids. Google+ Christopher Chang, MD Bio

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