Confusing reports of “allergic reactions” to COVID-19 vaccine.

Media reports this morning are suggesting that two National Health Service workers developed symptoms of “anaphylactoid reactions” after receiving the new Pfizer/BioNTech vaccine for COVID-19. The pair “responded adversely” following their shots, and were part of the several thousand who were vaccinated in the UK on Tuesday, the first day of the mass vaccination rollout, National Health Service England said Wednesday. Both of the patients with reactions reportedly had a history of anaphylaxis and carried an epinephrine autoinjector.

Pfizer COVID-19 vaccine.

Based on these reports, health officials in the United Kingdom have advised that people with a history of significant allergic reactions should not be given the new Pfizer/BioNTech vaccine for COVID-19. “As is common with new vaccines the MHRA [Medicines and Healthcare products Regulatory Agency] have advised on a precautionary basis that people with a significant history of allergic reactions do not receive this vaccination after two people with a history of significant allergic reactions responded adversely yesterday,” said Stephen Powis, the national medical director for NHS England, in a statement. “Both are recovering well.”

The MHRA also issued new advice to health care professionals stating that any person with a significant allergic reaction to a vaccine, medicine or food — such as previous history of anaphylactoid reaction, or those who have been advised to carry an adrenaline autoinjector — should not receive the Pfizer/BioNtech vaccine. The advice also states that vaccines “should only be administered in facilities where resuscitation measures are available.”

This is a very strange situation. The contents of this vaccine (see below) do not include any protein component that could cause a true allergic reaction. Also, there were no allergic reactions reported in the 44,000 individuals in the clinical trial. I worry that there was a problem with administration of the vaccine or some other unique aspect to this site.

Despite these reports I do not think that “anyone with a history of allergic reactions should not get this vaccine.” To reassure, in the US we almost uniformly give vaccines in facilities with resuscitation equipment available. Also, until these reports are validated, I think we should withhold judgment as to what caused these reactions. There are tests that can identify allergic reactions/mast cell activation, and these should be done. The patients need to be full evaluated given the consequences of making these statements.

Vaccine Composition:

The Pfizer-BioNTech COVID-19 Vaccine is a white to off-white, sterile, preservative-free, frozen suspension for intramuscular injection. The vaccine contains a nucleoside-modified messenger RNA (modRNA) encoding the viral spike glycoprotein (S) of SARS-CoV-2. 

The vaccine also includes the following ingredients: lipids ((4-hydroxybutyl)azanediyl) bis(hexane-6,1-diyl)bis(2-hexyldecanoate), 2-[(polyethylene glycol)-2000]-N,N-ditetradecylacetamide, 1,2-distearoyl-sn-glycero-3-phosphocholine, and cholesterol), potassium chloride, monobasic potassium phosphate, sodium chloride, dibasic sodium phosphate dihydrate, and sucrose. 

Published by jbakerjrblog

Immunologist, former Army MD, former head of allergy and clinical immunology at University of Michigan, vaccine developer and opinionated guy.

15 thoughts on “Confusing reports of “allergic reactions” to COVID-19 vaccine.

  1. Seems odd they would issue a blanket restriction for anyone with any serious allergies. I’m guessing that the people affected were asked about their known allergies and nothing matched the ingredients. It makes me think about cross-reactivity or even the theory of molecular mimicry in autoimmunity. Thank you for posting the list of ingredients. To me it just looks like a list of scientific words for sugar, salt and fats.

    Liked by 1 person

  2. I am a RN, trying to decide to get or not to get this vaccine. I was all on board to recieve this vaccine until today and then the concerns with the allergic reactions have me worried. I have tried to research the ingredidents in particular the lipid ingredients. I have food allergies that involve mammal ingredients called alpha-gal, which is caused from a tick bite. How can I find out it these lipid based ingredients are sourced from mammal? This allergy is a reaction to all mammal (beef, lamb, venison, pork, etc) which also includes milk based products. Gelatin which is mammal based can cause reactions in people with alpha-gal. Any information is greatly appreciated.

    Liked by 1 person

    1. Yes, alpha-gal is a well defined allergic problem. In addition, gelatin a stabilizer found in some formulations for injection, can be problematic. Fortunately, the Pfizer vaccine has no gelatin, and the lipids are synthetic. There is no source of alpha-gal in this vaccine, and the only stabilizer is sucrose (table sugar).


  3. Having suffered anaphylactic shock from a fish/seafood allergy I was alarmed by the news and the warning. I’m my 92 year old mother’s primary caregiver and hope to be vaccinated. Am I unduly nervous?

    Liked by 1 person

  4. Has any information been released on what exactly the 2 patients were allergic to? I have a severe nut allergy so I’m wondering specifically what they were allergic to.

    Liked by 1 person

  5. As someone else referenced, a publication online mentions that “A material used in the early stage of the manufacturing process of COVID-19 mRNA Vaccine BNT162b2 contains a component that is derived from bovine milk. The bovine milk is fit for human consumption and complies with bovine spongiform encephalopathy (BSE)/transmissible spongiform encephalopathies (TSE) regulations.”

    And yet, another article mentions that, “the contents of this vaccine do not include any protein component that could cause a true allergic reaction.”

    It’s a little confusing but just to confirm, should this be a cause for concern with those a dairy allergy?

    Liked by 1 person

  6. Should someone with a strong negative skin test reaction to propylene glycol be concerned re polyetheline glycol component present in Pfizer and Moderna vaccines?

    Liked by 1 person

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