Recently, we received some feedback on our article about the influenza shot being found to be safe for all people, including those who are allergic to eggs. One reader asked, “Why is the shot safe for people with an egg allergy now, when it wasn’t before?” Did something change in the vaccine formula? Was more research done that revealed new evidence? The answer is yes. Here is why.
Egg-Containing Vaccines: Now Considered Safe
In 2011, the Centers for Disease Control and Prevention (CDC) and the American Academy of Pediatrics (AAP) suggested that patients who were egg allergic should receive inactive influenza vaccine (IIV) annually like everyone else but with a few precautions. People who had had reactions to eggs of only hives were advised to receive their vaccination in a primary care setting where they could be observed for 30 minutes after the vaccination was administered. Patients who had previously experienced more severe reactions to egg were told to go to an allergist to receive their flu vaccine. Prior skin testing was also recommended before the vaccine was given to some patients.
In 2012 and 2013, updates were published that disclosed that the influenza vaccine IIV was now considered safe for people who are egg allergic, along with those who have a history of anaphylactic response to egg. The amount of ovalbumin, or egg protein, contained in each vaccine was now below 1 microgram/mL. This level is low enough that it is considered unlikely to generate an allergic response even in people who previously displayed the most severe reactions after ingesting egg.
The above guidelines only included IIV and not live attenuated influenza vaccine (LAIV). At the time, LAIV was not included in the guidelines. No studies had demonstrated safety for this vaccine, which also contains a low level of ovalbumin at less than 0.24 micrograms/mL, for egg-allergic people.
Since the 2013 update, both of the egg-containing influenza vaccinations, IIV and LAIV, have been announced to be safe in egg-allergic patients as the result of two large cohort studies that demonstrated that LAIV also was safe for egg-allergic individuals. The CDC and AAP have each updated their guidelines for the 2017-2018 influenza season.
New Non-Egg Vaccines
Not only have the guidelines changed for influenza vaccines that contain ovalbumin, but there have been additional developments in the realm of flu safety and egg allergy. Two more influenza vaccines have been introduced, both of which claim to be non-egg-based.
One vaccine known as ccIIV4 is approved for patients over the age of four and is grown in cell culture. There is a chance that this vaccine could contain 50fg (femtograms) of ovalbumin.
A second vaccine known as RIV is created in an insect cell line with recombinant hemagglutinin protein. This vaccine does not contain any egg protein and is approved for patients over the age of 18. It is available as quadrivalent RIV4 and trivalent RIV3.
Currently, the AAP guidelines state that all children with egg allergy can receive an influenza vaccine without any added precautions beyond those recommended for any vaccine for both egg-allergic and non-allergic people. No special precautions are warranted for IIV.
The CDC also asserts that people who have experienced any severity of allergic reaction to egg can receive the influenza vaccine as long as it is age appropriate. The CDC does go on to recommend that people who have had reactions to eggs with symptoms other than hives should receive the vaccine in a supervised medical setting.
Strong evidence suggests that egg-allergic individuals can take any of the influenza vaccines available today, including IIV, LAIV and the two non-egg-containing vaccines, regardless of their symptoms of allergic reaction to eggs. Screening prior to administration of vaccination is no longer required.
See also: Egg Allergy and the Flu Vaccine for more information.