Egg Allergy - Vaccine Hazard

Vaccine Hazard

The flu vaccine is typically made using chicken embryo, and as a result the final vaccine does contain egg proteins. Egg-allergic individuals may react to egg protein(s) in the vaccine (or to gelatin or neomycin if they are allergic to that). If an individual is unable to take the vaccine, vaccinating all other members of their family can help protect them from the flu.

Different brands and even individual batches of flu vaccine do vary in their egg protein content. Allergists formerly used skin testing with flu vaccine to predict if receiving the flu shot might be safe, but the results of this type of testing are totally unpredictive and this type of testing should be abandoned. Instead, the age-appropriate immunization material containing the lowest amount of egg proteins should be chosen, then a 1/10 dose should be given followed by a 30 minute observation period in a medical setting fully equipped to treat any possible reaction. Ovalbumin is usually used as a marker for the egg proteins. Vaccines available as recently as 2010 in the US contained up to 21 mcg of ovalbumin per 0.5 mL dose. In 2011 the ovalbumin content varies from less than 5.0 mcg/dose down to less than 0.05 mcg/dose, depending on the brand. One study done on 83 egg allergic patients resulted in a lack of serious reactions at doses of ovalbumin ranging from 0.10 mcg to 0.60 mcg. Thus so some brands available in the US in 2011 are probably safe for most egg allergic patients (administered with caution), but others may not be. For reference modern MMR vaccine (which is generally accepted now to be well tolerated by egg allergic patients, but which is still given with caution) was shown in a 2009 study reported in the BMJ to contain 0.0005 to 0.0010 mcg/dose [0.5 to 1.0 ng/dose). REFERENCE: June 2011 UPTODATE.com monograph on "influenza vaccine and egg allergy" and the NIH Expert Panel Report on Food Allergy, December 2010.

Egg proteins can also be found in yellow fever vaccine and MMR vaccine. The quantity of egg protein in a dose of MMR vaccine is approximately 40 picograms (much lower than in influenza vaccine, which contains approximately 0.02-1.0 micrograms), and this is believed to be associated with a much lower risk.