By: Alex Karamalegos.
Yearly vaccination against influenza plays a critical role in preventative medicine in our society today. The increased demand for influenza vaccines each year has not only expanded the access to vaccinations but it has also improved awareness and education. Despite the best efforts of healthcare teams, there will always be patients who choose not to receive the annual influenza vaccination; however, there is a subset of these patients who decline the vaccination for good reason—egg allergy. In November 2012, the US FDA approved Flucelvax, an egg-free flu vaccine for adults above the age of eighteen. Shortly after in January 2013, another egg-free vaccine, Flublok, was also approved by the US FDA for adults aged eighteen to forty-nine.
The egg component of the influenza vaccine originates from the chicken embryo fluid used to culture the vaccine. This process results in a very small amount of egg protein that can potentially induce an allergic reaction and in severe cases anaphylaxis. It is important to note that several other factors within the vaccine, such as preservatives or virus-inactivating agents, may also induce an anaphylactic reaction.
The new influenza vaccines were developed using alternative culture techniques aimed at eliminated the use of chicken embryo fluid. Flucelvax utilizes mammalian cell cultures, while Flublok takes advantage of recombinant DNA in an insect virus system. Each of these new vaccines is a trivalent inactivated influenza vaccine (TIV). The evidence supports the use of both egg-free vaccines with results that are comparable to the standard egg-containing vaccines. Flucelvax showed an efficacy of eighty-four percent when it was evaluated by seven randomized trials consisting of 6281 adult patients. In addition, the serious adverse reactions to the egg-free vaccines were also comparable to the egg-containing vaccines. Both vaccines are not approved for patients under eighteen years old due to lessened immunogenicity in this age group leading to decreased effectiveness.
Clinical Guidelines (in an eggshell):
Determining Egg Allergy:
- Patient with a history of egg allergy, but currently able to directly ingest eggs would no longer be considered to have an egg-allergy. Recommended to receive standard vaccine.
- Patient who is unable to tolerate direct ingestion of eggs, but is able to tolerate small amounts of eggs indirectly, such as within baked goods, would be considered to have an egg-allergy. Recommended to receive egg-free vaccine if available.
- Skin testing for egg-allergy is no longer recommended.
- Adults with established egg-allergy – Recommend administration of egg-free vaccine (in appropriate age groups). If egg-free vaccine is unavailable, proceed with standard egg-based vaccination with a 30-minute observation period in a facility prepared to treat anaphylaxis.
Disclaimer: Please note that the information above has been obtained from multiple sources for the sole purpose of student education and should not be used in the direct care of patients and/or clinical decision making.
1) Kelso, JM, Wang, J. Influenza vaccination in individuals with egg allergy. In: UpToDate, Basow, DS (Ed), UpToDate, Waltham, MA, 2013.