(Updated 9/5/2021) – Over 300 million doses of the Pfizer/BioNTech (also known as Comirnaty) and Moderna mRNA COVID-19 vaccines have been administered in the United States. There have been approximately 5 cases of a severe allergic reaction to these vaccines per 1 million doses administered. Approximately 90% of these reactions occurred within the first 30 minutes after injection. While we still do not know exactly what is causing all of these reactions, one of the potential culprits is polyethylene glycol. This article discusses polyethylene glycol allergy.
What is polyethylene glycol?
Polyethylene glycols (PEGs) are synthetic chemicals that are used frequently in our daily lives. PEGs are in medical products (e.g. wound dressings and laxatives), household products (e.g. detergents and polishes), food (e.g. preservatives and supplements), and cosmetic products (e.g. creams, facial products, and baby wipes).
PEG is used in the Pfizer and Moderna mRNA COVID-19 vaccines to protect the mRNA in the vaccine. It also helps to penetrate cells to jumpstart your immune system. The ingredients in the Pfizer COVID-19 and Moderna vaccines includes PEG-2000. The number following the PEG refers to the molecular weight of that substance.
How common is PEG allergy?
A review of the scientific literature reported 37 cases of an allergic reaction to PEG from 1977 to 2016. However, only 28 of these cases actually met the criteria for a severe allergic reaction (i.e. anaphylaxis).
Authors from a recently published report on PEG allergy concluded that the risk of developing an allergic reaction increases when the molecular weight of the PEG is high. None of the patients in this report reacted to PEG 2000, which is the molecular weight of PEG in the COVID-19 vaccines.
In other words, a PEG allergy is very rare!
Should I get tested for PEG allergy?
There is no commercially available blood test for PEG allergy at this time. While allergy skin testing to PEG has been tried in the past, PEG skin testing is not accurate. In fact, a recent study reported that the majority of patients who had an allergic reaction to the first dose of the vaccine were able to safely get a second dose regardless of PEG skin test results. Because of these recent research updates, our office currently does not offer this PEG skin testing.
Organizations such as the American Academy of Allergy, Asthma, and Immunology (AAAAI), FDA, and CDC are actively looking into these allergic reactions. They will create strategies to help reduce the risk of future reactions.
Oak Brook Allergists will continue to update you with important information regarding COVID-19 vaccines when it becomes available. If you have further questions, please request a consultation appointment by calling us at (630) 574-0460 or by filling out our appointment request form online now. We have convenient locations in Downers Grove, Elmhurst, Naperville, and Plainfield, Illinois.