Safety Concerns About the Pfizer Vaccine: The Pre-Licensure Data and Anaphylactoid Reactions in the UK

  • One dose is less reactogenic than two
  • Reduced limitations on patient compliance (patients don’t have to return for a second dose of the vaccine in 21 days)
  • You can immunize twice as many people with the same amount of vaccine, which means you can reduce the force of infection much more rapidly than with a two-dose regimen, even if a single-dose regimen is less effective


I would like to credit and extend my sincerest gratitude to my dear friend, Andrea Bailey PhD, Senior Regulatory Affairs Specialist, for once more using her prodigious expertise of pharmaceutical regulation to ensure the accuracy of this article and her thorough editing.


  1. ACIP contraindications guidelines for Immunization. 2020 Nov 18.
  2. Anagnostou K, Turner PJ. 2019. Myths, facts and controversies in the diagnosis and management of anaphylaxis. Arch Dis Child. 104(1):83–90.
  3. Bailey, Andrea, Written Correspondence, 12/9/20
  4. Choi KR. 2020. A nursing researcher’s experience in a COVID-19 vaccine trial. JAMA Intern Med. doi:10.1001/jamainternmed.2020.7087.
  5. Cody Meissner H, FAAP. 2020. Shoulder injury related to vaccine administration reported more frequently. AAP News.
  6. Guidance for Industry Toxicity Grading Scale for Healthy Adult and Adolescent Volunteers Enrolled in Preventive Vaccine Clinical Trials.
  7. Information for Healthcare Professionals on Pfizer/BioNTech COVID-19 vaccine.
  8. Kelso JM, Greenhawt MJ, Li JT, Nicklas RA, Bernstein DI, Blessing-Moore J, Cox L, Khan D, Lang DM, Oppenheimer J, et al. 2012. Adverse reactions to vaccines practice parameter 2012 update. J Allergy Clin Immunol 130(1):25–43.
  9. Kozma GT, Mészáros T, Vashegyi I, Fülöp T, Örfi E, Dézsi L, Rosivall L, Bavli Y, Urbanics R, Mollnes TE, et al. 2019. Pseudo-anaphylaxis to polyethylene glycol (PEG)-coated liposomes: Roles of anti-PEG IgM and complement activation in a porcine model of human infusion reactions. ACS Nano. 13(8):9315–9324.
  10. Office of the Commissioner. 2020 Aug 12. Emergency Use Authorization.
  11. Office of the Commissioner. 2020 Sep 9. What is a Serious Adverse Event?
  12. Pfizer-biontech covid-19 vaccine (bnt162, pf-07302048) vaccines and related biological products advisory committee briefing document.
  13. Regulatory Decision Summary — Pfizer-BioNTech COVID-19 Vaccine — Health Canada.
  14. Shellfish allergy is not a shell game.
  15. Study to Describe the Safety, Tolerability, Immunogenicity, and Efficacy of RNA Vaccine Candidates Against COVID-19 in Healthy Individuals.
  16. Vaccine safety and the management of adverse events following immunisation.
  17. Vaccines and Related Biological Products Advisory Committee Meeting December 10, 2020 FDA Briefing Document Pfizer-BioNTech COVID-19 Vaccine.
  18. Vial stoppers: The hidden latex risk in the perioperative environment — anesthesia patient safety foundation. 2015 Oct 10.
  19. Wadman M. 2020. United States wants to end most payouts for leading vaccination-related injury. Science. doi:10.1126/science.abc0484.
  20. Wenande E, Garvey LH. 2016. Immediate-type hypersensitivity to polyethylene glycols: a review. Clin Exp Allergy. 46(7):907–922.
  21. Working Group of the Resuscitation Council (UK). Emergency treatment of anaphylactic reactions Guidelines for healthcare providers.



Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store
Edward Nirenberg

Edward Nirenberg


I write about vaccines here. You can find me on Twitter @enirenberg and at (where I publish the same content without a paywall)