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Using Patients’ Allergy History as Screening Tool for mRNA COVID-19 Vaccine Works Well: Study

Jul. 27, 2021, 1:30 PM


by Nancy Humphrey

A report of more than 23,000 health care workers and employees at Vanderbilt University Medical Center who received the Pfizer-BioNTech mRNA COVID-19 vaccine shows that a risk stratification screening mechanism for potential allergies to the vaccine worked exceedingly well as the vaccine program rolled out in December 2020.

Out of the 23,035 health care workers and employees at VUMC who received the Pfizer vaccine between Dec. 17, 2020, and March 17, 2021, the screening identified only three individuals with a prior possible allergy history to an injectable medicine or vaccine. Each was pulled out of the pool and didn’t receive their vaccine that day, but all three received additional screening, and all went on to receive and tolerate the vaccine.

Elizabeth Phillips, MD

“In December 2020 when the Pfizer-BioNTech mRNA COVID-19 vaccine initially rolled out in the United Kingdom and the United States, there were reports of anaphylaxis that disproportionately affected women and those with an underlying allergic tendency, giving rise to some initial concern,” said Elizabeth Phillips, MD, John A. Oates Chair in Clinical Research, professor of Medicine, and lead author of the paper published in the Journal of Allergy and Clinical Immunology: In Practice.

“This was an incredible collaboration between VUMC’s Allergy and Immunology program and Occupational Health that allowed COVID-19 vaccination to proceed safely in health care workers and added to data suggesting that mRNA vaccines are overwhelmingly safe. Using a risk stratification program like this was very successful in being able to roll out vaccination without seeing much of any noise,” she said.

Phillips, an expert in drug hypersensitivity, said the study was conducted because of the concern of allergic reactions that had been reported after the Emergency Use Authorization (EUA) was established for the Pfizer vaccine. These had not been seen in the clinical trials of the Moderna and Pfizer COVID-19 mRNA vaccines, but the trials had excluded anyone who had a history of allergy to vaccines or those who had a reaction to a component of a vaccine.

“At this time there was a concern that polyethylene glycol (PEG) 2000, used to stabilize the lipid nanoparticle carrier system that carries the active mRNA component encoding spike protein of these vaccines, could be implicated,” she said.

“With these initial reports, the Centers for Disease Control and Prevention recommended caution and avoidance of vaccination with the mRNA vaccines in those with a history of injectable medication or vaccine anaphylaxis where PEG or polysorbate, a derivative of PEG, was present, but from our experience prior to COVID-19, the allergies were thought to be quite rare overall.

“It raised concern. What was going on, and was this going to be something that would be seen more commonly? Was it a risk?” Were patients with an underlying allergic tendency at risk?” Phillips said.

PEG has not been a part of vaccines in the past, but has been used in some injectable drugs. Polysorbate, a common component of many vaccines and injectable drugs, had not been a cause for concern in the past.

The risk stratification mechanism set up by Phillips and her team included having nurses and other volunteers working at the VUMC vaccine locations to page the fellow on call with the Division of Allergy, Pulmonary and Critical Care Medicine if there was a concern.

“We put together a ‘traffic light’ document that could be followed in the vaccine hall to identify those in the ‘red traffic light zone’ with a potential history of PEG sensitivity. If volunteers were checking people in and identified someone who could be at risk, the Allergy service would be called to give an opinion on whether the individual could be vaccinated right then and there or sent home for follow-up and a potentially specialized work-up or observed COVID-19 vaccination at the Allergy Clinic,” Phillips said.

Of 23,035 screened prior to dose one of the vaccine, 31 reported a higher-risk allergy history that triggered a focused review by the allergist-on-call. Of the 31 with a high-risk allergy history, 28 were recommended to proceed with dose one without any delay, based on the screening process. Of the 28 high-risk allergy workforce members who proceeded to the first dose of the vaccine, none were later referred by Occupational Health for evaluation of a dose-one adverse reaction. The remaining three received additional screening, then received their first dose.

“The screening algorithms employed for the vaccine allergy risk assessment prior to administration of the first dose of the Pfizer vaccine were integral to the rollout, but we have come a long way, and these can now be revised based on insights gained on epidemiology and mechanisms,” Phillips said.

Phillips and colleagues at 29 centers across the United States are also conducting an NIH-funded study to determine the mechanisms of COVID-19 mRNA vaccine allergy. The study is ongoing and those who have not yet been vaccinated and are interested in participating can find out more information from or by contacting

Others from VUMC who contributed to this work are: Matthew Krantz, MD, Cosby Stone Jr., MD, MPH, Grace Koo, MD, Kristen Corey, MD, Sara Bluestein, MD, Patrick Staso, MD, Emily Campbell, MD; Lori Rolando, MD, MPH, and Ana Nobis, MD.

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