Non–immunoglobulin E-mediated allergy associated with Pfizer-BioNTech coronavirus disease 2019 vaccine excipient polyethylene glycol

The development of safe and efficacious coronavirus disease 2019 (COVID-19) vaccines has been pivotal in nanomedicine research, helping to curtail further spread of the severe acute respiratory syndrome coronavirus 2 virus. Although severe immunologic reactions to the vaccine are rare, fear of allergic reactions impedes global vaccination efforts. Understanding the mechanism of these allergic reactions is important for informing guidelines, including contraindications, to COVID-19 vaccines and for the development of next-generation vaccines with improved safety. We introduce a severe case of a non–immunoglobulin E (IgE)-mediated hypersensitivity resulting in an immediate-type reaction to the Pfizer-BioNTech COVID-19 vaccine. A 56-year-old woman received her first dose of the Pfizer-BioNTech messenger RNA (mRNA) vaccine (BNT162b2). Approximately 5 minutes after administration, she felt dizzy, lightheaded, dyspneic, throat tightening, and abdominal pain. Initial blood pressure was 145/94 mm Hg; a repeat reading minutes was later done with a blood pressure of 70/42 mm Hg and a pulse rate of 150 beats/minute. Her physical examination was notable for faint end-expiratory wheezes. Her systolic blood pressure further fell to the 50s and a code blue was called for additional resources. Intramuscular epinephrine was administered immediately after code blue team arrival and after 2 minutes, her blood pressure recovered to 176/77 mm Hg. Although her symptoms transiently improved, she continued to have waves of chest tightness and dyspnea requiring 2 subsequent doses of 0.3 mg of intramuscular epinephrine followed by a 20-µg bolus of epinephrine intravenously, and initiation of an epinephrine infusion at 0.1 µg/kg/min. In addition, she received lactated ringer's solution, racemic epinephrine and albuterol nebulizer, famotidine, diphenhydramine, and methylprednisolone (Methylprednisolone, Pfizer, New York, New York), and was admitted to the intensive care unit. In the intensive care unit, her vital signs improved, and she was weaned off of the epinephrine infusion 3 hours later. She did not require supplemental oxygen and her wheezing resolved. Tryptase level was collected approximately 90 minutes after the index event, which was 6 ng/mL (reference range < 11.5 ng/mL). There were no further objective signs of a biphasic or protracted anaphylactic reaction, and she was ultimately discharged from the hospital after 5 days with epinephrine injector pens. The patient was instructed not to receive the second dose of the Pfizer-BioNTech vaccine and was enrolled in the national vaccine adverse event reporting system. Allergy testing was pursued on a follow-up clinic visit after 21 days. The patient received skin prick testing (SPT) to undiluted BNT162b2 vaccine, polyethylene glycol (PEG) (a small lipophilic excipient in both Pfizer-BioNTech and Moderna vaccines), and polysorbate 80 (a known cross-reactant to PEG). Histamine and normal saline were used as positive and negative controls, respectively. Whole blood was obtained from the patient, and activation markers, which are up-regulated on basophils during a hypersensitivity reaction, were measured in vitro using flow cytometry. Blood was heparinized, stored in a 4°C cold room on a rocker, and aliquoted and analyzed within the same day. Dilutions of dimyristoyl glycerol-polyethylene glycol (DMG-PEG) 2000 (Avanti Polar Lipids, Alabaster, Alabama) were prepared and then stored at 4°C. Using sterile tubes, 100 µL of heparinized blood was stimulated with 100 µl of saline, a DMG-PEG dilutant (0.002 µg/µl), or with 1 µL of BNT162b2. Cells were stained with a viability dye (Zombie NIR Fixable Viability Kit, BioLegend, San Diego, California) and an antibody panel consisting of anti–CD63-FITC, anti–HLA-DR-PR, and anti–CD123-PerCP/Cy5.5 (Becton Dickinson, Franklin, New Jersey) using standardized published procedures.1Mukai K Gaudenzio N Gupta S et al.Assessing basophil activation by using flow cytometry and mass cytometry in blood stored 24 hours before analysis.J Allergy Clin Immunol. 2017; 139 (e11): 889-899Abstract Full Text Full Text PDF PubMed Scopus (68) Google Scholar Cells were counted by means of flow cytometry with the BD FACSCanto II Cell Analyzer (Becton Dickinson Immunocytometry Systems, San Jose, California) and analyzed with FlowJo Software (FlowJo LLC, Ashland, Oregon). Using the patient's sera, enzyme-linked immunosorbent assay was performed to detect anti-PEG antibodies. Enzyme-linked immunosorbent assays were developed with anti-PEG human-6.3-Immunoglobulin G (IgG) with a cutoff optical density (OD405) of 0.4 and anti-PEG human-6.3-IgE with a cutoff OD405 of 0.2. Anti-PEG IgE and IgG standards were used (Academia Sinica, Taiwan). The SPT result was interpreted as negative to BNT162b2, DMG-PEG, and polysorbate 80. Basophils were detectable in the patient's samples and activated basophils were gated as CD63-positive (CD63+), CD123-positive, and HLA-DR–negative. For blood stimulated with DMG-PEG 2000 or BNT162b2, 29.1% and 23.3% of basophils, respectively, were CD63+, compared with 3.129% in the saline control group (Fig 1). Samples of the patient's sera tested with anti-PEG human-6.3-IgG and anti-PEG human-6.3-IgE resulted in titers below cutoff values. Polyethylene glycol is a vaccine stabilizer used in the Pfizer-BioNTech and Moderna mRNA COVID-19 vaccines and is thought to be a major contributing allergen.2Sellaturay P Nasser S Islam S Gurugama P Ewan PW. Polyethylene glycol (PEG) is a cause of anaphylaxis to the Pfizer/BioNTech mRNA COVID-19 vaccine.Clin Exp Allergy. 2021; 51: 861-863Crossref PubMed Scopus (177) Google Scholar It has never previously been included in approved vaccines, but it serves as an excipient in a number of medicines, foods, and cosmetics. Activation of the patient's basophils on exposure to the vaccine excipient PEG implicates PEG as a potential allergen. However, given the low anti-PEG titers, the reaction seems to be non-IgE- and non–IgG-mediated anaphylaxis. The tryptase from the index event was negative; however, negative tryptase after a case of anaphylaxis to the Pfizer vaccine has been described.2Sellaturay P Nasser S Islam S Gurugama P Ewan PW. Polyethylene glycol (PEG) is a cause of anaphylaxis to the Pfizer/BioNTech mRNA COVID-19 vaccine.Clin Exp Allergy. 2021; 51: 861-863Crossref PubMed Scopus (177) Google Scholar Skin prick testing performed on the patient to the vaccine, DMG-PEG 2000, and polysorbate 80 all had negative results. Although we did not test multiple molecular weights of PEG, there is evidence that PEG2000 (molecular weight 2000 Da) found in the vaccine can result in negative SPT despite clinical anaphylaxis to PEG.2Sellaturay P Nasser S Islam S Gurugama P Ewan PW. Polyethylene glycol (PEG) is a cause of anaphylaxis to the Pfizer/BioNTech mRNA COVID-19 vaccine.Clin Exp Allergy. 2021; 51: 861-863Crossref PubMed Scopus (177) Google Scholar, 3Stone Jr, CA Liu Y Relling MV et al.Immediate hypersensitivity to polyethylene glycols and polysorbates: more common than we have recognized.J Allergy Clin Immunol Pract. 2019; 7 (e8): 1533-1540Abstract Full Text Full Text PDF PubMed Scopus (253) Google Scholar, 4Wenande E Garvey LH. Immediate-type hypersensitivity to polyethylene glycols: a review.Clin Exp Allergy. 2016; 46: 907-922Crossref PubMed Scopus (266) Google Scholar Furthermore, higher molecular weight PEGs may have a lower reactivity threshold.4Wenande E Garvey LH. Immediate-type hypersensitivity to polyethylene glycols: a review.Clin Exp Allergy. 2016; 46: 907-922Crossref PubMed Scopus (266) Google Scholar Anaphylaxis to PEGylated compounds is unusual but has been reported in the literature, including 53 unique cases identified by Stone et al3Stone Jr, CA Liu Y Relling MV et al.Immediate hypersensitivity to polyethylene glycols and polysorbates: more common than we have recognized.J Allergy Clin Immunol Pract. 2019; 7 (e8): 1533-1540Abstract Full Text Full Text PDF PubMed Scopus (253) Google Scholar from the Food and Drug Administration Adverse Event Reporting System between 1989 and 2017, and similarly, 37 cases identified by Wenande and Garvey4Wenande E Garvey LH. Immediate-type hypersensitivity to polyethylene glycols: a review.Clin Exp Allergy. 2016; 46: 907-922Crossref PubMed Scopus (266) Google Scholar between 1977 and 2016. Case reports of suggested IgE-mediated hypersensitivity to PEG provide some insights; however, PEG-specific IgE is often not detectable, which may, in some circumstances, result from a lack of assay sensitivity.4Wenande E Garvey LH. Immediate-type hypersensitivity to polyethylene glycols: a review.Clin Exp Allergy. 2016; 46: 907-922Crossref PubMed Scopus (266) Google Scholar, 5Wylon K Dölle S Worm M. Polyethylene glycol as a cause of anaphylaxis.Allergy Asthma Clin Immunol. 2016; 12: 67Crossref PubMed Scopus (64) Google Scholar, 6Giangrande N García-Menaya JM Marcos-Fernández M Cámara-Hijón C Bobadilla-González P Anaphylaxis due to macrogol in a laxative solution with a positive basophil activation test.Ann Allergy Asthma Immunol. 2019; 123: 302-304Abstract Full Text Full Text PDF PubMed Scopus (11) Google Scholar, 7Zhou ZH Stone Jr, CA Jakubovic B et al.Anti-PEG IgE in anaphylaxis associated with polyethylene glycol.J Allergy Clin Immunol Pract. 2021; 9 (e3): 1731-1733Abstract Full Text Full Text PDF PubMed Scopus (98) Google Scholar In other cases, PEGylated lipid nanoparticles may activate host immune defense through non-IgE pathways such as Mas-related G protein-coupled receptor X2–mediated direct mast cell and basophil degranulation and complement activation–related pseudoallergy to PEG.8Risma KA Edwards KM Hummell DS et al.Potential mechanisms of anaphylaxis to COVID-19 mRNA vaccines.J Allergy Clin Immunol. 2021; 147 (e2): 2075-2082Abstract Full Text Full Text PDF PubMed Scopus (105) Google Scholar,9Klimek L, Novak N, Cabanillas B, Jutel M, Bousquet J, Akdis CA. Allergenic components of the mRNA-1273 vaccine for COVID-19: possible involvement of polyethylene glycol and IgG-mediated complement activation [e-pub ahead of print]. Allergy. https://doi:10.1111/all.14794, accessed September 3, 2021.Google Scholar Recent data reported the tolerability of a second dose COVID-19 mRNA vaccine with an antihistamine or steroid premedication in those with convincing immediate hypersensitivity reactions to the first dose.10Wolfson AR Robinson LB Li L et al.First-dose mRNA COVID-19 vaccine allergic reactions: limited role for excipient skin testing.J Allergy Clin Immunol Pract. 2021; 9 (e3): 3308-3320Abstract Full Text Full Text PDF PubMed Scopus (110) Google Scholar This suggests a role for possible second or booster dose of mRNA vaccine or alternative Janssen COVID-19 vaccine under an allergist's supervision for those with vaccine-associated PEG hypersensitivity. We would like to thank Theo Snow, Mihir Shah, and Anja Heider for assistance gathering data and conducting experiments. We would like to thank Vanitha Sampath for manuscript editing.