ACAAI Revises Guidelines for Allergic Reactions Following COVID-19 Vaccines

The American College of Allergy, Asthma and Immunology (ACAAI) has updated their guidelines regarding the risk of allergic reactions following administration of the COVID-19 vaccine now include information on screenings, observation periods, and the option of forgoing the second dose following a documented allergic reaction from the first dose.

The ACAAI’s COVID-19 Vaccine Task Force has monitored real-time data from sources reporting allergic reactions following the COVID-19 vaccine to reflect the most recent recommendations from the US Centers for Disease Control and Prevention (CDC) and the US Food and Drug Administration (FDA).

New Guidance

The new guidelines call for patients to be screened to determine the possible risk of an allergic reaction to any of the 3 vaccines and be referred to a board-certified allergist or immunologist for further evaluation if the individual has a history of severe allergic reactions.

In accordance with CDC guidance, anyone individual who had a severe or immediate allergic reaction of any severity within 4 hours of receiving the first COVID-19 dose should not get the second dose.

In addition, patients who experienced a severe or immediate allergic reaction of any severity, including hives, swelling, or wheezing, or who have questions related to the risk of an allergic reaction should be referred to a local board-certified allergist/immunologist to provide more care or advice.

In general, the vaccines should be administered in a health care setting where anaphylaxis could be treated and all recipients should be observed for 15-30 minutes following an injection. The majority of reported anaphylaxis cases have occurred within 15 minutes of administration.

Finally, neither the mRNA or adenovirus vector vaccines should be administered to individuals with a known history of severe allergic reactions to any component of a particular vaccine.

Allergic Reactions

While the specific component that causes anaphylaxis has yet to be identified, polyethylene glycol (PEG), a component in the 2 mRNA vaccines has been known to cause anaphylaxis. In addition, polysorbate 80, an ingredient in the Johnson & Johnson vaccine, could cause anaphylaxis and cross-react with PEG.

Patients with allergic reactions to PEG should not be administered the mRNA vaccines, but consideration could be given to vaccination with adenovirus vector vaccines.

Currently the CDC recommends the adenovirus vector vaccines as a replacement for the second dose of an mRNA vaccine for patients who had a reaction to the first dose, waiting at least 28 days between doses.

According to CDC guidance, polysorbate allergies are no longer a contraindication to mRNA vaccination, but it is a precaution and because of potential cross-reactive hypersensitivity between ingredients in mRNA and adenovirus vector vaccines, consultation should be considered. Also, for patients with a polysorbate allergy, there should be a minimum of a 30 minute observation period following an mRNA vaccine.

There is also very limited, but evolving data on the risk for patients with a history of allergic reactions related to mast cell activation syndrome/idiopathic anaphylaxis.

Current data shows allergic reactions to all vaccines are generally rare, with the occurrence of anaphylaxis estimated to be 1.31 in 1 million doses. For the first 2 COVID-19 vaccines to receive an Emergency Use Authorization (EUA) by the FDA, the anaphylaxis rates as of Jan 29 were 5 per million with the Pfizer-BioNTech mRNA-based vaccine and 2.5 per million for the Moderna vaccine.

The anaphylaxis rates for the recently approved Johnson & Johnson vaccine have yet to be reported.