Report of severe allergic reaction to SARS-CoV-2 mRNA vaccines

The recent agreement on two novel RNA (mRNA) true coronavirus respiratory syndrome 2 (SARS-CoV-2) vaccines by various regulatory bodies has given hope that we may finally end the disease- spread that caused more than 100 million diseases and claimed more than 2.3 million lives worldwide.

The first vaccine approved to prevent COVID-19 (Pfizer-BioNTech) began in the UK in December 2020. Within days, there were reports of two or possibly three anaphylactic reactions following the vaccine. The same vaccine was administered with an emergency use license (EUA) by the U.S. Food and Drug Administration (FDA), and again, within days, there were reports of at least two anaphylactic reactions. A second mRNA (Moderna) vaccine has now been approved.

Statement by John M. Kelso, Department of Allergy, Asthma and Immunology, Scripps Clinic, published in the latest issue of the journal Vaccines, considering anaphylactic reactions to these novel SARS-CoV-2 / COVID-19 mRNA vaccines.

Anaphylaxis is a multifactorial event that occurs due to the release of histamines and other mediators from mast cell granules and can be fatal. Pre-exposure to allergens can produce IgE antibodies, which are secreted by mast cells. When a person repeats the allergen, these antibodies are released into the livers and into the blood.

Mast cells are found mainly in the skin and in the respiratory and gastrointestinal tracts. Symptoms of anaphylactic reactions include skin rash, coughing, wheezing, abdominal pain, and nausea. The reaction can be fatal due to asphyxiation of the upper airway, severe bronchospasm, or very low blood pressure.

In general, anaphylactic reactions to vaccines are very rare, occurring at a rate of about 1 per million. However, the reports on COVID-19 vaccines indicate that these reactions have a higher-than-normal level of reactions. Ongoing studies by manufacturers and regulatory bodies are trying to determine if these are allergic reactions and determine which part of the vaccine is an allergen.

Demonstrating anaphylactic reactions to vaccines

This must first examine whether the timing and symptoms are consistent with a diagnosis for anaphylactic reaction. IgE-mediated reactions usually occur within minutes of exposure to the allergen, so any sensory reaction to the vaccine should be apparent shortly after administration. vaccine.

If the symptoms after vaccination are consistent with anaphylactic reaction, the next step is to check for IgE antibodies. Given that the approved vaccines are new, it is unlikely that the patients were previously exposed to IgE antibodies, but may have been sensitive to some part of the vaccine.

The modified mRNA vaccines encode the spike protein of true respiratory coronavirus syndrome 2 (SARS-CoV-2). Part of the vaccines, polyethylene glycol (PEG), has been reported to cause IgE-mediated reactivation and is considered a potential allergen. PEG is widely used in a number of pharmaceuticals, cosmetics, and foods, and such exposure may have been noticed by some patients. Therefore, these vaccines may be unsuitable for these rare individuals with PEG allergy.

Vaccines should be given in a position that allows observation after injection to allow appropriate treatment for any allergic reaction, such as epinephrine administration. After that, testing blood samples for mast cell tryptase may allow further diagnosis, a high level indicating an allergic reaction, although normal levels are not ruled out.

Investigating potential allergens

Following reports of anaphylactic reaction to the Pfizer vaccine, the UK Medicines and Healthcare products Regulatory Agency (MHRA) has issued guidance that the vaccine should not be given to anyone with a relapse. -recognizable exposure to any vaccine, medication or food. In the United States, the Centers for Disease Control (CDC) has stated that anyone with a history of severe allergic reactions should be monitored for 30 minutes after vaccination and others for 15 minutes. minute.

Although PEG is suspected, there may be other allergens. However, because PEG allergies are very rare and people who may be bothered may feel irritated without getting any reaction, it can be challenging to identify who which may interfere with the pre-vaccination, if PEG is indeed the allergen.

Patients who have had a first – dose anaphylactic reaction should not receive the second – dose vaccine. Other vaccines being developed are different from the mRNA vaccines, and these patients may receive a different vaccine.

“Although anaphylaxis is a potentially life-threatening event, it is always successfully treated, and its risk must be weighed against leaving patients unvaccinated and therefore vulnerable. for a potentially life-threatening disease, COVID-19, ”the author wrote.

Investigations into the likely anaphylactic reactions should be carried out promptly and thoroughly to reduce the number of patients who may be experiencing a severe reaction and not to avoid eliminated by those who received no response and who may be protected from COVID-19.