Allergy to COVID-19 vaccines: A current update

Abstract

Adverse allergic reactions due to the administration of the vaccines developed for the protection of coronavirus disease 2019 (COVID-19) have been reported since the initiation of the vaccination campaigns. Current analyses provided by the Center for Disease Control and Prevention (CDC) and Food and Drug Administration (FDA) in the United States have estimated the rates of anaphylactic reactions in 2.5 and 11.1 per million of mRNA-1273 and BNT162b2 vaccines administered, respectively. Although rather low, such rates could have importance due to the uncommon fact that a large majority of the world population will be subjected to vaccination with the aforementioned vaccines in the following months and vaccination will most likely be necessary every season as for influenza vaccines. Health regulators have advised that any subject with a previous history of allergy to drugs or any component of the vaccines should not be vaccinated, however, certain misunderstanding exists since allergy to specific excipients in drugs and vaccines are in occasions misdiagnosed due to an absence of suspicion to specific excipients as allergenic triggers or due to inaccurate labeling or nomenclature. In this review, we provide an updated revision of the most current data regarding the anaphylactic reactions described for BNT162b2 vaccine, mRNA-1273 vaccine, and AZD1222 vaccine. We extensively describe the different excipients in the vaccines with the potential to elicit systemic allergic reactions such as polyethylene glycol (PEG), polysorbates, tromethamine/trometamol, and others and the possible immunological mechanisms involved.

Keywords: Anaphylaxis; COVID-19; SARS-CoV-2; Vaccine allergy; Vaccines.

Fig. 1

Chemical structures of polysorbate 80 and PEG. The shared structures of polysorbate 80 and polyethylene glycol are included in rectangles in the chemical structure of polysorbate 80.

Fig. 2

Active components and full list of excipients of the vaccines. Potential triggers of allergic reactions are indicated in red color in the lists. The principles of the PEGylated-lipid nanoparticles as a delivery system for the mRNA is depicted in the lower part for BNT162b2 and mRNA-1273 vaccines. The replication-deficient adenovirus ChAdOx1 vector for the AZD1222 vaccine is also depicted. Biorender software was used to create this figure under an academic license.

Fig. 3

Chemical structures of ethylene oxide, ethylene glycol and PEG.