A report based on more than 23,000 healthcare 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 well as the vaccine program rolled out in December 2020.
Out of the 23,035 healthcare 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 his or her vaccine that day, but all three received additional screening, and all went on to receive and tolerate the vaccine.
Elizabeth Phillips, MD, 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.
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.
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.