One year of research establishes COVID-19 vaccine safety among patients with allergies
One year of research establishes COVID-19 vaccine safety among patients with allergies

One year of research establishes COVID-19 vaccine safety among patients with allergies

April 18, 2022

2 min read


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The Allergy and Immunology Society has made significant and hopeful progress in its understanding of allergic reactions to mRNA COVID-19 vaccines, according to a review published in Journal of Allergy and Clinical Immunology.

Although reports of anaphylaxis accompanied the earliest doses administered in December 2020, evidence now shows that these cases are rare, Aleena Banerji, MD, associate professor at Harvard Medical School and clinical director of the Allergy and Clinical Immunology Unit at Massachusetts General Hospital, and colleagues wrote in the review.




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Early in the rollout of the vaccines, the authors wrote, the polyethylene glycol (PEG) 2000 molecule, which stabilizes the lipid nanoparticle carrier of the active mRNA encoding the SARS-CoV-2 peak protein, was proposed as the trigger for immediate allergic reactions to these. vaccines.

The CDC and the FDA, as well as international regulatory bodies, initially recommended that people with PEG allergies refrain from mRNA vaccination. However, research has since found that individuals with previous anaphylactic reactions to PEG or PEG derivatives can tolerate mRNA vaccines.

The authors also wrote that individuals who presumably had an anaphylactic reaction to the first dose of an mRNA vaccine largely tolerate second and booster doses, suggesting mechanisms not mediated by IgE.

In fact, the authors wrote, many of these immediate reactions to the first dose were experienced without any objective hypersensitivity symptoms and were vasovagal, symptomatic stress reactions, reactogenic or syncopal rather than allergic.

The authors also wrote that patients who have a reaction to an mRNA vaccine do not need PEG skin testing, which may delay the completion of the vaccination. Many of these patients have probably tolerated subsequent doses as well, with allergic supervision.

Further, the authors pointed to the need for reduce hesitation with vaccines among those patients with an allergy history. Booster shots reduce the severity of the disease among patients receiving variants such as delta and omicron, the authors wrote. There is now also a shortage of new monoclonal antibodies used for acute treatment or pre-exposure prophylaxis of COVID-19 omicron cases.

Some theoretical evidence indicates that PEG IgM and IgG may cause non-IgE-mediated mechanisms, although the authors called such tests unlikely to be useful in predicting mRNA vaccine responses.

In addition, some people may have reactogenic symptoms associated with the active components of the vaccines that reveal underlying tendencies towards non-IgE-mediated mast cell activation. Underlying anxiety about vaccination and other various factors can also trigger non-allergic symptoms.

Although true responses to mRNA vaccines are rare, the authors continued, physicians should observe vaccination and handle these cases carefully while considering skin prick tests for PEG and for the vaccines.

The authors also encouraged allergy sufferers to work up individuals who have previously had PEG anaphylaxis, whether or not they have tolerated mRNA vaccines, as they are still at risk of potentially fatal anaphylaxis due to PEG3350, which has a higher molecular weight.

The authors noted that allergy is almost never a reason for exceptions to the COVID-19 vaccines, and the authors wrote that no history, including food, medicine, vaccine, or other allergies, is a contraindication to vaccination.

Finally, the authors wrote that co-decision is key and encouraged physicians to cite published data on tolerance of mRNA vaccines despite previous reactions when discussing risks and benefits of vaccination with their patients.

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