Egg allergy and influenza vaccine

Unfortunately, all influenza vaccines carry the admonition that egg allergic individuals may react to their administration. STOP….before reading any further, make sure you have a true egg allergy before you worry about the influenza vaccine.  Many patients have a positive TEST to eggs, but eat them just fine without any symptoms.  This isn’t an allergy and you have no need to worry about avoiding sunny side up  for breakfast. You do need to still get your flu shot!

There are no exceptions to this since all such vaccines are grown on media which may contain egg allergen. As always, there are clearly alternatives that are available to, in the vast majority of instances, allow the administration of influenza vaccine to egg allergic individuals.  In fact, new guidelines recommend giving the Flu vaccine even if you are allergic to egg….it’s tolerated very well and allergic reactions are quite rare (see below).

That makes me hungry

If you’re concerned, such patients can be tested to egg and influenza vaccine; testing & desensitization is usually highly successful in allowing the safe administration of influenza vaccine under these circumstances.

 Listed below are clinical studies demonstrating that patients with egg allergy can safely receive the influenza vaccine: J Allergy Clin ImmunolVolume 121, Issue 2, Supplement 1, Page S240 (February 2008).

Zeiger RS. Current issues with influenza vaccination in egg allergy. JACI 2002;110:830-40

J Allergy Clin Immunol Volume 123, Issue 2, Supplement, Page S175 (February 2009).

Soooo….how about some history of influenza vaccine? The original injectable influenza vaccine was developed at the University of Michigan in the mid-1940s. The vaccine was made by taking influenza virus, injecting it into embryonated hen’s eggs (see picture), and letting the virus grow in the chorioallantoic cells that surrounded the yolk sac. They harvest the egg, purify the virus, and kill the virus with formaldehyde. I’m sure this is more than anyone wants to know, but since the vaccine was made in eggs, a certain amount of contaminating egg protein, specifically, ovalbumin was always still present.

What do we do, then, about children and adults who are severely allergic to egg proteins? 

1.   During the last 15 years, we have gotten much better at protein purification, protein chemistry, and being able to purify the inactivated virus or the live attenuated virus without using ovalbumin. Thus, there is much, much less ovalbumin in current vaccines. (The quantity of egg protein in vaccine is expressed as the concentration of ovalbumin per dose or unit volume.  Check the package insert to find out if ovalbumin is < 1.4μg/mL; reaction rates are much less below this threshold)

2.  Children with egg allergy can receive the vaccine, but the Advisory Committee on Immunization Practices does recommend that, as a precaution for those who have more severe allergic manifestations like hives (or worse), those children should be given the vaccine in the presence of an allergist or someone who knows what to do should there be an anaphylactic reaction.  I think that’s a good idea.

3.  Ultimately, we will probably give the influenza vaccine much as we give the measles vaccine to children who are egg allergic now. Carefully, but most tolerate both vaccinations just fine.

Want more information–>check out the following resources:

 American Academy of Allergy

Prevention and Control of Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices (ACIP), 2011. MMWR Morbid Mortal Wkly Rep. [Early release: August 18, 2011.] Available at: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm60e0818a1.htm?s_cid=mm60e0818a1_w Accessed August 22, 2011.

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