Some of the hype and hype surrounding the approval of COVID vaccines has been fueled by recent reports of allergic problems. Twenty cases of confirmed anaphylaxis have been identified after the first 1.8 million doses of the Pfizer-BioNTech vaccine were given (approximately 1 in 87,000 injections). Although rare, this is significantly higher than the risk associated with other vaccines (1.3 per million).
To date, most anaphylaxis episodes have occurred within 30 minutes of receiving the vaccine and were easy to treat. Out of 21 case reports identified, five patients had food allergies, and three of them had a history of drug allergy. A total of 12 patients had an allergic reaction to medications or vaccines, and one patient had environmental allergies.
As for the Moderna vaccine, one or two cases of facial depression have occurred without side effects. The Centers for Disease Control and Prevention (CDC) now recommends a short period of post-vaccination observation in a facility that is feasible and ready to treat anaphylaxis.
So what are the most likely causes of these reactions, and how can we keep our patients safe? Here are the answers to some questions you may have.
Are vaccine allergies common?
Vaccine allergy is very rare. The antigen of these rare allergic reactions to vaccines is usually not an antigen but an additive – an additive that may include antibiotics, preservatives, or adjuvants. . Meat proteins (gelatin and, very rarely, alpha-gal) have also been identified as causes of IgE-mediated reactivation in vaccines with higher gelatin content (MMR and VZV). Thus, in some cases, atopy (especially food allergy) may be a risk factor for reactions to certain vaccines. Influenza vaccines contained in eggs, on the other hand, contain so few egg allergens that it is no longer a concern for patients with even egg allergy.
What may be causing COVID-19 vaccine anaphylaxis?
It has recently been suggested that the cause of these reactions is the polyethylene glycol (PEG) allergen, which is present in both the Moderna and Pfizer vaccines to help stabilize the mRNA. PEG has been identified as a cause of recurrence on colonoscopy preparation; stool softeners (such as Miralax); and medications, including standard and parenteral corticosteroids, as well as PEG-coated tablets and toothpaste. The high molecular weight of PEG may be immunogenic. Both IgE and IgG antibodies to these excipients, along with advanced skin tests, support this.
Who is at risk for COVID-19 vaccine anaphylaxis?
This is yet to be confirmed and may be different for each COVID-19 vaccine. Acting under the assumption that the agent is causal May be PEG, then patients with a suspicious history of IgE-mediated reactions to stool softener, colonoscopy preposcopy, and other outcomes in which PEGylated results may be compromised.
How do you assess patients who may be at risk?
Skin testing and intradermal testing to PEG-3350 (the polyethylene glycol in stool softener Miralax) have been reported and were positive in some patients with a history of anaphylaxis for this result; the skin test resulted in moderate urticarial rash with dyspnea and diffuse pruritus. With at least some experience with a PEG skin test, this may be done in patients with a questionable history of PEG allergy. But how it would go beyond that would still be an unrecorded area.
How should we manage higher risk patients?
The CDC recommends that patients with an anaphylactic reaction to the first dose of the COVID-19 vaccine not receive the second dose. When there is doubt about the diagnosis – for example, in the setting of a possible vasovagal immunosuppression – serum tryptase dose (SC5b-9, the termination filler) may confirm a diagnosis anaphylaxis. I advise interpretation of the test result in consultation with an allergist-immunologist. A history of anaphylactic reaction to any polysorbate (such as PEG) also contradicts the Pfizer and Moderna vaccines.
How should we manage patients with vaccines?
The Johnson & Johnson COVID-19 vaccine uses adenovirus vector rather than mRNA. For patients a May have received anaphylaxis after the first dose but in which the reaction is highly in doubt, an allergist may consider performing a scratch test with serial challenge. There is debate as to whether that is worth the risk, as the first dose of vaccine has moderate efficacy and another vaccine is on the horizon.
Gary J. Stadtmauer, MD, is an allergist-immunologist in New York City. Areas of clinical interest include asthma, eczema, chronic cough, and sinusitis. He has been a Medscape partner since 2014.
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