Originally posted January 18, 2021; most recently updated August 20, 2021
The following information is provided for clinicians.
NOTE – This was on the CDC website and may be helpful to clinicians:
Health care personnel or health departments in the United States can request a consultation from the Clinical Immunization Safety Assessment COVID vax project for a complex COVID-19 vaccine safety question about an individual patient residing in the United States not readily addressed by CDC guidance.
Q: What are the ingredients in the Pfizer-BioNTech COVID-19 Vaccine?
1. Active ingredient: nucleoside-modified messenger RNA (modRNA) encoding the viral spike (S) glycoprotein of SARS-CoV-2.
2. Inactive ingredients: Lipids ((4-hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate), [(polyethylene glycol [PEG])-2000]-N,N-ditetradecylacetamide, 1,2-distearoyl-sn-glycero-3-phosphocholine, and 0.2 mg cholesterol), Electrolytes potassium chloride, monobasic potassium phosphate, sodium chloride, dibasic sodium phosphate dihydrate, Sugar (sucrose)
The diluent, added to the vaccine for administration, is saline (Sodium Chloride).
Q: What are the ingredients in the Moderna COVID-19 Vaccine?
1. Active ingredient: Messenger ribonucleic acid (mRNA)
2. Inactive Ingredients: Lipids (SM-102, polyethylene glycol [PEG] 2000 dimyristoyl glycerol [DMG], cholesterol, and 1,2-distearoyl-sn-glycero-3-phosphocholine [DSPC]), Tromethamine, Tromethamine hydrochloride, Sodium acetate, Sugar (sucrose)
Q: What are the ingredients in the Johnson & Johnson COVID-19 Vaccine?
1. Active ingredient: adenovirus vector Ad26.COV2.S carrying the viral spike (S) glycoprotein of SARS-CoV-2
2. Inactive ingredients: Citric acid monohydrate, Trisodium citrate dihydrate, Alcohol, Hydroxypropyl betadex, Polysorbate 80, Sodium chloride, Sodium hydroxide, Hydrochloric acid, Water
Q: What is PEG?
A: Polyethylene glycol (PEG) is a common, water-soluble ingredient in a wide variety of commercial products including some vaccines and more than 1,000 FDA approved medications. It is present in both the mRNA-based Pfizer/BioNTech and Moderna vaccines. It is the primary ingredient in commonly used colonoscopy preparations (Golytely) or constipation treatment (Miralax) as well as in IV medications such as PEGylated medications. It is also in ultrasound gel and injectable steroid injections such as methylprednisolone acetate. Reactions to polyethylene glycol are exceedingly rare but anaphylaxis has been reported. Polysorbate, present in the adenovirus vector-based Johnson & Johnson vaccine, is structurally related to PEG and cross-reactivity can occur. Polysorbate allergy is considered a contraindication to receiving either the mRNA or adenovirus-based vaccines.
Contact dermatitis to PEG
A history of contact dermatitis (rash with exposure or history of positive patch testing) to PEG or to a related compound including polysorbate is not a contraindication to getting the COVID-19 vaccines. No cross reactivity has been demonstrated between propylene glycol and PEG derivatives.
Systemic reactions to PEG
The most commonly known clinical use of polyethylene glycol is PEG 3350 in colonoscopy preparations or constipation treatment (e.g. Miralax). However, PEG and structurally similar polysorbate compounds can be found in vascular graft materials, surgical gels, PEGylated medications, household and industrial compounds, and as an excipient in a multitude of other medications, both injectable and oral.
A recent review of published case reports and case series in the literature by Garvey et al., found 37 cases of PEG hypersensitivity since 1977. A review of the FDA data by Stone et al., adds a large number of additional cases that may not have been noticed in the medical literature. Their data suggests an average of four cases per year of PEG-associated anaphylaxis during colonoscopy preparation or laxative use are reported to the FDA. The review of FDA adverse event data focused only on drugs that contained pure PEG 3350 at concentrations of grams per dose. To determine clinical reactivity to macrogols, including PEG and polysorbate containing products, Stone et al., used a combination of skin prick, intradermal and challenge testing with standard methodologies. Little is known about cross reactivity among the different molecular weights of PEG for both contact dermatitis and immediate hypersensitivity reactions, but it is likely that molecular weight is an important factor. The molecular weight of PEG in the Pfizer and Moderna COVID vaccines is 2,000.
Patch testing may evaluate for contact dermatitis to PEG in personal products. Chemotechnique Diagnostics has a commercially available PEG patch test (molecular weight PEG 400) and polysorbate 80 (same molecular weight in the Johnson & Johnson vaccine). Immediate hypersensitivity reactions are typically evaluated by skin prick and intradermal tests, which to date have not been standardized for PEG or polysorbate. There are some testing protocols that have been published in the medical literature that can be considered specifically for the evaluation of IgE mediated allergy to PEG with the caveat that a negative skin test result does not rule out allergy: Skin testing could be negative because it’s a false negative (using non-irritating skin test concentrations) or because the individual doesn’t have an IgE mediated allergy or because the allergic reaction to the first dose was related to complement activation-related pseudoallergy (CARPA).