Most People With PEG Allergy or Reactions to First COVID-19 Shot Can Still Complete Vaccine Series

Esther Landhuis

November 06, 2021

Editor's note: Find the latest COVID-19 news and guidance in Medscape's Coronavirus Resource Center.

With the rollout of COVID-19 vaccines, there's been concern about possible allergic reactions to polyethylene glycol (PEG), an ingredient used to stabilize lipid nanoparticles in the Moderna and Pfizer-BioNTech's mRNA vaccines. Two posters presented at this year's American College of Allergy, Asthma and Immunology annual meeting show that allergists can help safely assess whether people who are allergic to PEG can receive a COVID-19 shot, and whether individuals who reacted to the first dose can take a second.

The new studies also suggest that "most patients in each category will be able to safely take the COVID-19 vaccine," Brian Schroer, MD, director of allergy and immunology at Akron Children's Hospital in Ohio, told Medscape Medical News.

In the first study, researchers led by allergy fellow Mitchell Pitlick, MD, at the Mayo Clinic in Rochester, Minnesota, combed Epic electronic health records for 100 adults with a PEG allergy documented prior to receiving a COVID-19 vaccine. As part of this retrospective chart review, the team collected information on demographics, comorbidities, atopic history, PEG allergy history, and vaccination outcome. Ninety-seven patients received mRNA vaccines (64 Pfizer-BioNTech vaccine, 33 Moderna), and three got the Johnson & Johnson vaccine.

Among those 100 adults, most of the symptoms in response to PEG-containing drugs occurred with oral preparations (84%), and the vast majority of these were reported as gastrointestinal intolerance with no other symptoms, indicating they were probably not true allergic reactions, said Pitlick. Five percent of patients had anaphylaxis listed as a reaction symptom for their PEG allergy. Yet these five individuals received a COVID-19 vaccine — four getting Pfizer-BioNTech and the other a Johnson & Johnson shot — and did fine. In fact, all 100 patients in the study tolerated the COVID-19 vaccine series without any allergy symptoms.

This study suggests that "just because you have an allergy label to PEG doesn't mean you need to be turned away from receiving an mRNA COVID-19 vaccine," Pitlick said, noting that one of his patients received both doses of the Pfizer vaccine with no issues despite having had three separate episodes of anaphylaxis to PEG-containing devices and medications.

In a multisite US study published July 26 in JAMA Internal Medicine, even an immediate allergic reaction to the first dose of an mRNA COVID-19 vaccine did not keep patients from getting a second dose. Among the 84% who proceeded, 12% reported mild symptoms but all were able to safely complete their vaccination series.

The second study, presented by allergy fellow Jennifer Ohtola, MD, PhD, and colleagues at the Cleveland Clinic in Ohio, assessed the utility of PEG oral challenges in patients evaluated for COVID-19 mRNA vaccine allergy. The team reviewed charts to assess COVID-19 vaccination outcomes of 63 patients who underwent PEG/polysorbate 80 skin testing from January through June 2021 either because they were concerned prevaccination about previous adverse reactions to vaccines, medications, or PEG/polysorbate (n = 38) or reported a reaction to the first COVID-19 mRNA vaccine dose (n = 25).

In total, only five of 63 patients (7.9%) had a positive PEG skin test — and of the two who additionally underwent an oral challenge, both had symptoms. This is consistent with the low sensitivity and high specificity of PEG skin testing in other studies. In this study, "patients who had negative skin testing and PEG oral challenge were able to receive a COVID-19 mRNA vaccine safely," said Ohtola.

Among those who were PEG skin test negative, more than half who reported symptoms during their PEG oral challenge went on to tolerate COVID-19 mRNA vaccines. On the flip side, three patients with negative PEG skin testing subsequently reported allergic reactions during vaccination. These anomalies raise the question "if PEG is really to blame for mRNA vaccine reactions," Pitlick told Medscape Medical News.

Still, Ohtola said, the findings suggest that "PEG oral challenge can provide additional guidance for patient and allergist in the shared decision-making process of receiving COVID-19 vaccination."

Schroer has received consulting fees from Sanofi and Ready, Set, Food for matters unrelated to COVID-19 or drug allergies.

American College of Allergy, Asthma and Immunology: ePoster P003, ePoster P006. Presented November 5, 2021

Esther Landhuis is a freelance science journalist in the San Francisco Bay Area. She can be found on Twitter @elandhuis.

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