Peter Vadas MD, PhD Consultant in Allergy and Clinical Immunology
Pfizer COVID Vaccine and Anaphylaxis

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Anaphylactic reactions to the Pfizer COVID Vaccine
The immunogen in the Pfizer-BioNTech COVID-19 Vaccine is a nucleoside-modified messenger RNA (modRNA) encoding the viral spike glycoprotein (S) of SARS-CoV-2 
The non-medicinal constituents of the Pfizer COVID-19 vaccine are:

  • ALC-0315 = (4-hydroxybutyl) azanediyl)bis(hexane-6,1-diyl)bis(2- hexyldecanoate)
  • ALC-0159 = 2-[(polyethylene glycol)- 2000]-N,N-ditetradecylacetamide
  • 1,2-distearoyl-sn-glycero-3- phosphocholine
  • cholesterol
  • dibasic sodium phosphate dihydrate
  • monobasic potassium phosphate
  • potassium chloride
  • sodium chloride
  •  sucrose
  • water for injection
Common sources of exposure and sensitization to PEG

  • Food products
  • Industrial products
  • Cosmetic products
  • Medications
  • Toiletry products
  • Pharmaceutical products
Medications: PEG-asparaginase; PEGylated-IFN alpha; PEG-filgrastim; Peginesatide; pegvaliase-pqpz
certolizumab pegol; Movicol; macrogol in laxative solutions;  [ 99m Tc]-labeled nanocolloidal albumin (Nanocoll ®); fosaprepitant; cabazitaxel; Depo-Medrol; Lipegfilgrastim; PEGylated liposomal doxorubicin (Doxil); Pegloticase; Polysorbate in Omalizumab; recombinant Factor VIII

Note:  This is a partial list of medications containing PEG and its analogues.  Check with your physician and pharmacist for other medications and preparations potentially containing polyethylene glycol.
One of the major allergenic components of the Pfizer COVID vaccine is polyethylene glycol (PEG)

Polyethylene Glycol

PEG has been implicated in causing allergic reactions ranging from mild hives to life-threatening anaphylaxis.

Sellaturay P, Nasser S, Ewan P. Polyethylene Glycol-Induced Systemic Allergic Reactions (Anaphylaxis). J Allergy Clin Immunol Pract. 2020 Oct 1:S2213-2198(20)31007-2. doi: 10.1016/j.jaip.2020.09.029. Epub ahead of print. PMID: 33011299.

Jover Cerdá V, Rodríguez Pacheco R, Doménech Witek J, Marco de la Calle FM, de la Sen Fernández ML. Immediate hypersensitivity to polyethylene glycols in unrelated products: when standardization in the nomenclature of the components of drugs, cosmetics, and food becomes necessary. Allergy Asthma Clin Immunol. 2019 Feb 19;15:9. doi: 10.1186/s13223-019-0327-4. PMID: 30820197; PMCID: PMC6381633.

Polyethylene glycol is a derivative of ethylene oxide. 

PEG goes by a number of different names, which include:
  • macrogols
  • oxyethylene polymer
  • laureth-9

PEG derivatives include
  • poloxamer-407
  • polysorbate 80

There is one report of hexyldecanoic acid in lipstick causing contact dermatitis: Kimura M, Kawada A. Contact dermatitis due to 2-hexyldecanoic acid (isopalmitate) in a lipstick. Contact Dermatitis. 1999 Aug;41(2):99-100. doi: 10.1111/j.1600-0536.1999.tb06235.x. PMID: 10445691.

Before being given the Pfizer COVID vaccine or any other injectable drug or vaccine, please review with your physician if you have known allergies to any component of the vaccine.  If you may have an allergy to a vaccine component, discuss the relative risks and benefits of immunization.

Ensure that the facility giving the vaccine has the resources and expertise to recognize and treat anaphylactic reactions.

Wait in the clinic for a minimum of 30 minutes following immunization.