The CDC recently published vaccine recommendations for the 2013-4 influenza season (http://www.cdc.gov/flu/about/season/index.htm). Special attention is given to those patients with a history of egg allergy.
Influenza vaccine is grown in embryonated chicken eggs and contains residual amounts of ovalbumin, a major egg allergen. For patients with egg allergy, even small amounts of this protein can trigger an allergic reaction. This risk must be considered before vaccination . On the other hand, Influenza infection poses a significant risk itself. There are approximately 300,000 hospitalizations annually, including more than 20,000 in children younger than 5. Children with asthma are most vulnerable. This is concerning given the increased incidence of asthma in children with egg allergy.
Due to fear of allergic reaction, flu shots were previously withheld from all children with egg allergy. In order to assess risk, allergists began skin testing children with the influenza vaccination. In 1977 physicians began immunizing those egg allergic children with a negative influenza skin test. About ten years later another group pushed further. This time, children with a positive skin test were successfully vaccinated using a multi-step protocol. The most recent studies (including those with H1N1 vaccine) have found the real risk of reaction to be exceptionally low. One recent study, vaccinated 143 children with documented severe egg allergy. No children had a significant allergic reaction take place. This data is prompting change. Beginning with the 2011-2012 season, the AAP, CDC/ACIP, and NIAID specifically recommend that patients with egg allergy receive the trivalent inactivated influenza vaccine (TIV) with some precautions.
Here is a quick summary of the most recent CDC recommendations:
1. Persons with a history of egg allergy who have experienced only hives after exposure to egg should receive influenza vaccine.
– Vaccine should be administered by a healthcare provider who is familiar with the potential manifestations of egg allergy; and
– Vaccine recipients should be observed for at least 30 minutes for signs of a reaction after administration of each vaccine dose .
2. Persons who report having had reactions to egg involving such symptoms as angioedema, respiratory distress, lightheadedness, or recurrent emesis; or who required epinephrine or another emergency medical intervention may receive egg-free vaccines, if aged 18 through 49 years and there are no other contraindications. If egg-free vaccines are not available or the the receipient is not within the indicated age range, such persons should be referred to a physician with expertise in the management of allergic conditions for further risk assessment before recipient of vaccine.
– All vaccines should be administered in settings in which personnel and equipment for rapid recognition and treatment of anaphylaxis are available.
3. For individuals who have no known history of exposure to egg, but who are suspected of being egg-allergic on the basis of previously performed allergy testing, consultation with a physician with expertise in the management of allergic conditions should be obtained prior to vaccination.
4. A previous severe allergic reaction to influenza vaccine, regardless of the component suspected to be responsible for the reaction, is a contraindication to future receipt of the vaccine.
Beyond the recommendations:
– Egg-free vaccines may be used for persons aged 18-49 years who have no other contraindications. In 2012, the FDA approved Flucelvax, the first influenza vaccine produced without egg. A second vaccine, FluBlok, was approved in 2013.
– Skin testing is NO longer routinely necessary for patients with egg allergy. However, skin testing with the vaccine IS still appropriate when evaluating a patient with a history of reaction to the influenza vaccine itself, as opposed to a history of reaction to egg.
– Studies have shown ovalbumin (egg) content up to 1.2 ug/ml to be well tolerated. Most available vaccines have significantly less.
– Although intranasal vaccine (FluMist) contains one of the lowest absolute amounts of ovalbumin per dose, there are no data on its administration to patients with egg allergy. Thus, injectable vaccine only should be used for patients with egg allergy.