key: cord-1051223-bqiw16i7
authors: Klimek, Ludger; Novak, Natalija; Cabanillas, Beatriz; Jutel, Marek; Bousquet, Jean; Akdis, Cezmi A.
title: Allergenic components of the mRNA‐1273 vaccine for COVID‐19: possible involvement of polyethylene glycol and IgG‐mediated complement activation
date: 2021-03-03
journal: Allergy
DOI: 10.1111/all.14794
sha: d67a8499c3fbcea91c51b1abbfd636b43c9e0bb8
doc_id: 1051223
cord_uid: bqiw16i7

Following the emergency use authorization of the mRNA‐1273 vaccine on the 18(th)of December2020,two mRNAvaccinesare in current use for the prevention of coronavirus disease 2019 (COVID‐19). For both mRNA vaccines, the phase IIIpivotal trials excluded individuals with a history of allergy tovaccine components.Immediately after the initiation of vaccination in the United Kingdom, Canada, and the US, anaphylactic reactions were reported. While the culprit trigger requires investigation, initial reports suggested the excipient polyethylene glycol 2000 (PEG‐2000) ‐contained in both vaccines as the PEG‐micellar carrier system ‐ as the potentialculprit. Surface PEG chains form a hydrate shell to increasestability and prevent opsonization. Allergic reactions to such PEGylated lipids can be IgE‐mediated,but may alsoresult from complement activation‐related pseudoallergy (CARPA) that has been described insimilar liposomes. In addition, mRNA‐1273 also contains tromethamine (trometamol), which has been reported to cause anaphylaxis to substances such asgadolinium‐based contrast media. Skin prick, intradermal and epicutaneoustests, in vitro sIgE assessment, evaluation ofsIgG/IgM,as well as basophil activation tests are being used to demonstrate allergic reactions to various components of the vaccines.

On the 18 th of December2020,an emergency use authorization (EUA) provided by the US Food and Drug Administration (FDA) permittedthe immediate use of the mRNA-1273 vaccinedeveloped by Moderna Therapeutics for the prevention of coronavirus disease 2019 . TheEUA allowed the immediate distribution and use of the mRNA-1273COVID-19 vaccine in the United States in subjects 18 years of age and older [1] .Itis the second vaccine to be granted an EUA by US regulators after the authorization received by Pfizer-BioNTech on the 11th of December 2020 for the use of theBNT162b2vaccine [2] . The authorization of mRNA-1273was based on early phase trials [3, 4] and on therevision of the results of an ongoing phase III trial that involved 33,000 adult subjects, randomized 1:1 to receive themRNA-1273vaccine in a two-dose regimen or placebo. The assessment performed by the FDA demonstratedthat the vaccine was 94.1% effective for the prevention of COVID-19 as determined 14 Allergic reactions to vaccines including severe anaphylaxis are generally IgE-mediated [10, 11] .They usuallyoccur within the first 30 minutes after vaccination and can be fatal.The symptoms include urticarial rashes, generalized pruritus, erythema, wheezing, coughing, dyspnea, throat, tongue, or eye swelling (angioedema), hypotension, dizziness, and vomiting.Furthermore, IgGand complement-mediated anaphylaxis-like reactionshave been described [12, 13] . Clinical symptoms of this non-IgE-mediated hypersensitivity include, among others, hypo-and hypertensionas well as airway obstruction with dyspnea [14] .Severe anaphylactic reactions to

This article is protected by copyright. All rights reserved vaccines are rare, and the rate has been estimated at 1.31 (95% CI, 0.90-1.84) per million vaccine doses [15] .

The frequency of allergic reactionstoBNT162b2was nearly the same in both the verum and placebo groups (0,6% versus 0,5%) [16] .

Allergicreactions to the mRNA-1273 vaccine have not been reported in detail. During the phase I trial of the mRNA-1273 vaccine, one case of transient urticaria in the verum group treated with a vaccine dose of 25µg was reported after the first injection. The total number of participants in this phase I trial was 45 [17] .

BothBioNTech/Pfizer and Modernaexcluded individuals with a history of allergic reaction to vaccines or their components from thephase IIItrials.The exclusion criteria for mRNA-1273 state:"History of anaphylaxis, urticaria, or other significant adverse reaction requiring medical intervention after receipt of a vaccine" [18] . 

This article is protected by copyright. All rights reserved Lipid nanoparticles are similar to liposomes, which have been in usepharmaceutically for many years as carriers for drugs. Some of the approved liposome/LNP-containing drugs also contain a PEGylated lipid (e.g. in Caelyx pegylated liposomal ® or Onpattro ® ). The PEG chains on the surface form a hydrate shell around the liposome/LNP. This increases stability and prevents opsonization, i.e. the mechanism by which the surface of foreign cells (e.g. bacteria, viruses) that have invaded the body is covered with antibodies and factors of the complement system. In addition, the stability and half-life of the lipid particles are increased. CARPAis partly attributed to the binding of pre-existing anti-PEG IgM to the liposomes with subsequent complement activation [40] . Clinical symptoms of this non-IgE-mediated hypersensitivity have been described as hypo-and hypertension, airway obstruction with dyspnea and other anaphylaxis symptoms shortly after the intravenous administration of liposomecontaining drugs [12, 33, 34, 41, 42] . Independent of PEGylation, liposomes have the potential to activate complement, non-specifically depending on their different surface structures and charge [12, 36] .Complement products C3a, C4a, and C5a (anaphylatoxins) are considered to be particularly important mediators.In addition to basophils, neutrophils and macrophages are also

This article is protected by copyright. All rights reserved considered to be relevant effector cells that can be activated via immune complex receptors (CD16, CD32, and CD64, respectively)[9, 12, 13, 35] .Anaphylatoxinsare liberated during complement activation [38, 43] .

Possible sensitization to PEG by previous use of cosmetics or drugs containing PEG is conceivable. Little is known about the prevalence of anti-PEG antibodies in the population.

Certainreports state that as much as 72% of the population have at least some IgG or IgM antibodies against PEG [44] , while others report high levels in healthy people and even in those without documented treatment with PEGylated products[37, 45, 46] .However, there is no evidence for allergy or anaphylaxis depending on IgG in man.Evidence for a possible role of IgE in triggering PEG-induced hypersensitivity is also being discussed [47] [48] [49] . Allergic reactions following the use of PEG as an excipient in a variety of products have been described.Thisis also referred to as a "hidden" allergen [47] [48] [49] [50] . (Figure 1 ). It should be noted that PEGshavenever been used in any vaccine,and that both Pfizer-BioNTech and Modernaare the first to apply this substance. PEGis ahydrophilic polyether compound used as an additive in medical productsand cosmetics [51] . It is branded under different names,e.g. macrogol. The molecular weight of the different PEGexcipients varies from 300g/mol to 10,000g/mol or higher.

Furthermore, hypersensitivity reactions may occur to the PEG of all molecular weights, with a higher rate of reaction to molecular weights of between3350 and 6000 g/mol [47] .However, it has been suggested that the molecular weight threshold for PEG immediate reactionsis still undetermined [48, 52] .

Cross-reactivity between PEG and its derivatives -i.e., structurally related polymers such as polysorbates -exists due to shared moieties (=CH 2 CH 2 and =CH 2 CH 2 OH) [47] .Severe allergic reactions to PEG, although rare, have been described after the administration of medications that contain this excipient.PEG has even been described as the high-risk hidden allergen, since it is difficult to detect as a possible cause of allergic reaction[30, 47, 48, 52, 53] .PEGylation isused successfullyfor drug delivery to protect the drug from any damage bythe immune system and to deliver it to the targeted location. In addition, PEG is anadditivein cosmetics and shampoos. Both

This article is protected by copyright. All rights reserved a primary cutaneous sensitization pathway and sensitization after systemic administration are possible [48] .

Additionally, and unlike the Pfizer-BioNTech vaccine, mRNA-1273 contains tromethamine, also calledtrometamol (molecular formula: C 4 H 11 NO 3 ), an organic amine that is widely used in several medications for topical, enteral, or parenteral administration. Tromethamine/trometamol is also used in cosmetic products as an emulsifier, and contact sensitization and allergy to this compound Risk factors exacerbating allergic reactions need to be taken into account when noting the medical history, such as previous anaphylaxis, mastocytosis or other mast cell diseases (Fig. 2) .

This article is protected by copyright. All rights reserved Allergy testing shouldbe performed in specialized allergy centers.Skin prick testsshould be performed very carefully:initial dilutions from 0.001% up to10% and a 30-minute observation period after every dose stepto minimize the risk of a systemic reaction to PEG. Since it has been speculated that the individual threshold for positive reactions to PEG of different molecular weights varies [52] , testing should be performed with PEG excipients of 2000g/molmolecular weightthat are used in both vaccines.Published algorithmsshould also be followed [52] . Skin tests should be performed not earlier than 2weeks after the hypersensitivity reaction. In addition, basophil activation tests(BATs)[8, 40]and screening for specific IgE to PEG in blood serum [8, 40] maybe performed in high-risk individuals andin patients with suspected allergy to excipients of the vaccine[8]. If PEG allergy can be confirmed, an emergency kit should be prescribed, and a PEGallergy information sheet provided. If not, intradermal testing with PEG of different molecular weights at a dilution of 0.01% can be carefully considered.High-risk patientsshould be excluded from those testingbecause systemic reactions can occur [8, 52] . In some settings, oral provocation tests can be performed if necessary [47] .

Trometamol as a contact sensitizer is usually tested epicutaneously for allergic reactions of the delayedtype. Testing for suspected type 1 reactions can be done by the skin prick procedure (concentration 1:1) followed by intradermal testing with dilutions of trometamol from 1:1000 to 1:10[55, 59].

Although allergic reactions tomRNA-1273 components such as PEG andtrometamolhave not been frequently reported, thefact that the COVID-19 vaccines will be extensively administrated worldwide to a high proportion of the population should caution healthcare providers of the potential allergic reactions that may occur in individuals previously sensitized to the components of the vaccines, especially to PEG and PEG analogues as well as to trometamol in the case of mRNA-1273[60].

This allergy is of particular interest since some of the drugs used to treat anaphylactic reactions, such as antihistamines or injectable corticosteroids, contain PEG or polysorbates. Substances that are cross-reactive to PEG, i.e., polysorbates[27], are widely distributed and commonly used in bread, pastry, chewing gum, ice cream, etc.They arealso present in a high number of vaccines, biologics, and mediations to treat rheumatologic, cardiovascular, hematologic, gastrointestinal, or Accepted Article oncologic diseases, and during diagnostic procedures.It is very likely that hypersensitivity reactions to such agents have been underestimated in the past.

Two doses of the vaccine must be administered to achieve an effect.Sensitization might occur during the administration of the first dose, or individuals may develop allergic reactions to the second dose.Whether the new route of delivery of PEG via intramuscular injection plays a rolein

its allergenicityhas yet to be determined. Since both mRNA-1273 and BNT162b2 contain PEG-2000, PEG-allergic patients, or patients allergic to components that are cross-reactive to PEG should be vaccinated with alternative COVID-19vaccines.Physicians should be aware of this potential risk and should interrogate thoroughly for previous allergic reactions to PEG, PEG analogues, or tromethamine.They should also be trained to respond to potential anaphylactic reactions during vaccination. In these patients, the administration of emergency medications containing PEG should be avoided. Alternatives should be considered, such asclemastine solution for intravenous injection, cetirizine syrup for oral intake, soluble prednisolone or methylprednisolone for oral intake or injection, and, of course, as recommended for all patients with severe anaphylaxis, most importantly, adrenaline [52] . 

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