Study: Nearly all severely allergic people tolerate COVID vaccines

While healthcare workers at a Boston healthcare system with severe allergies reported more reactions after receiving a COVID-19 mRNA vaccine, nearly all were able to safely complete the series, according to an observational study yesterday in JAMA Network Open.

Researchers at Mass General Brigham and Harvard Medical School mined the electronic health records of 52,998 employees, of whom 97.6% received both doses of vaccine, and 0.9% reported a history of high-risk allergy. The study period was Dec 14, 2020, to Feb 1, 2021. Participants completed a prevaccination allergy risk assessment and at least one postvaccination symptom survey during the 3 days after vaccination.

Current contraindications to COVID-19 mRNA vaccination include a history of severe or immediate allergic reactions to any vaccine component or to a previous dose of an mRNA vaccine. The employees, however, were given the vaccine according to Centers for Disease Control and Prevention guidelines, allergist consultation, risk stratification, and shared decision-making.

Rate of severe reactions: 0.3%

Allergic symptoms emerged more often after the first rather than the second dose. Most symptoms were mild (eg, rash, itching), at 2.7%, but respiratory symptoms (1.3%), hives (0.9%), and angioedema (swelling of the face, lips, eyes, or tongue) (0.6%) were also reported.

Severe allergic reactions were rare (0.3%). Of the 140 participants who reported severe allergic symptoms after vaccination, 4.3% had a history of high-risk allergy. The risk of a severe allergic reaction after vaccination was 1.3% among workers with a high-risk allergy history and 0.3% among those who had never had a high-risk reaction.

Relative to workers without allergies, those with severe allergies had more reactions after receiving one or two vaccine doses (11.6% vs 4.7%). After adjustment, high-risk allergy was tied to increased risk of reactions (adjusted relative risk [aRR], 2.46; 95% confidence interval [CI], 1.92 to 3.16). Risks were highest for hives (aRR, 3.81; 95% CI, 2.33 to 6.22) and angioedema  (aRR, 4.36; 95% CI, 2.52 to 7.54).

"However, reported allergy symptoms did not impede the completion of the 2-dose vaccine protocol among a cohort of eligible health care employees, supporting the overall safety of mRNA COVID-19 vaccine," the study authors wrote.

Participants were, on average, 42 years old, and 72% were women. Women and Black participants made up much higher proportions of those with a history of severe allergy than those with no history of allergy (80.8% vs 71.9% and 9.5% vs 4.8%, respectively).

Severely allergic vaccinees were older than those with no allergy history (46 vs 42 years on average), had more atopic (allergic) skin conditions (16.7% vs 8.7%), anxiety (28.9% vs 23.9%), high blood pressure (14.6% vs 10.9%), and cancerous tumors (4.0% vs 2.4%).

Participants at highest risk of allergic reactions to the vaccine were Black (RR, 1.69), had a higher Charlson comorbidity index score (RR, 1.04), and received the Moderna rather than the Pfizer vaccine (RR, 1.49). Compared with women, men were at decreased risk for a reaction (RR, 0.66).

Among 474 employees with a history of severe allergy, 46.6% had a previous reaction to an unknown or known allergen (eg, food, venom, drug, latex). Nearly 46% of these workers reported a previous severe allergic reaction to an injectable medication or vaccine. Only 1.9% had a previous severe allergic reaction to polyethylene glycol (PEG) (an inert vaccine ingredient) or PEG-containing products (eg, Miralax, injectable steroid).

People with history of reactions should consult allergist

Soon after the US Food and Drug Association issued an emergency use authorization for the mRNA COVID-19 vaccines from Pfizer/BioNTech and Moderna in December 2020, several severe allergic reactions were reported, raising concerns about vaccine safety, the researchers noted.

Since then, the reported rate of allergic reactions to these vaccines has been about 2%, and anaphylaxis (a severe, potentially life-threatening allergic reaction) has been estimated to occur in 0.025 to 2.47 cases per 10,000 vaccinations—or a 0.02% risk on the high end of that range. Of vaccinees who experienced anaphylaxis after vaccination, about a third had a history of the reaction.

Whether severe allergies are linked to allergic reactions after mRNA vaccination is still unclear, the authors noted, because the observed reactions may not be true allergies. People with a history of severe allergy to PEG should consult their allergist or immunologist before seeking COVID-19 vaccination; such an allergy may not be a contraindication for vaccination.

"Identification of risk factors for allergy symptoms after COVID-19 vaccination will guide safe vaccination practices for individuals at the highest risk and inform strategies that target vaccine hesitancy that is associated with allergy concerns," the researchers wrote.

Overall, the results are reassuring for people who have a history of severe allergy, senior author Kimberly Blumenthal, MD, said in a Massachusetts General Hospital news release.

"We hope these data will help inform ongoing conversations with patients who are hesitant to receive COVID-19 vaccination due to allergy concerns," she said. "At our institutions, nearly all individuals with and without a history of high-risk allergy were able to complete the two-dose vaccine series."

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