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Allergic Reactions to COVID-19 Vaccines

Severe allergic reactions to vaccines and vaccine components are very rare.

Two of the first people to get a new COVID-19 vaccine in the UK reportedly had allergic reactions.

Which had many people surprised that two of the first people to get a new COVID-19 vaccine in the UK reportedly had allergic reactions…

Allergic Reactions to COVID-19 Vaccines

What is it in vaccines that can trigger allergies?

“Any medication can cause a severe allergic reaction. Such reactions to a vaccine are estimated at about 1 in a million doses, and would happen within a few minutes to a few hours after the vaccination.”

Possible Side-effects from Vaccines

In general, components of vaccines can rarely allergic reactions include antibiotics, eggs, gelatin, latex, milk, and yeast. And again, severe, anaphylactic reactions to vaccines are very rare.

So what about the COVID-19 vaccines?

“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.”

FDA Briefing Document Pfizer-BioNTech COVID-19 Vaccine

There is not much in them that you would expect to trigger an allergic reaction.

Note that although polysorbate is not an ingredient in either the Pfizer or Moderna COVID-19 vaccines, but according to the CDC, "Polyethylene glycol (PEG), an ingredient in both mRNA COVID-19 vaccines, is structurally related to polysorbate and cross-reactive hypersensitivity between these compounds may occur."
Note that although polysorbate is not an ingredient in either the Pfizer or Moderna COVID-19 vaccines, but according to the CDC, “Polyethylene glycol (PEG), an ingredient in both mRNA COVID-19 vaccines, is structurally related to polysorbate and cross-reactive hypersensitivity between these compounds may occur.”

No antibiotics.

No yeast.

No preservatives.

No aluminum.

Could you be allergic to the nucleoside-modified messenger RNA (modRNA) encoding the viral spike glycoprotein?

Or the lipids and cholesterol that encapsulate the mRNA?

“FDA independently conducted standard MedDRA queries (SMQs) using FDA-developed software (MAED) to evaluate for constellations of unsolicited adverse event preferred terms that could represent various diseases and conditions, including but not limited to allergic, neurologic, inflammatory, and autoimmune conditions. The SMQs, conducted on the phase 2/3 all-enrolled safety population, revealed a slight numerical imbalance of adverse events potentially representing allergic reactions, with more participants reporting hypersensitivity-related adverse events in the vaccine group (137 [0.63%]) compared with the placebo group (111 [0.51%]).”

FDA Briefing Document Pfizer-BioNTech COVID-19 Vaccine

Maybe the lipids (PEG), but it is important to note that allergic reactions were very low in the clinical trials for this vaccine.

“Both vaccines consist of a snippet of genetic code directing production of the coronavirus’ spike protein, delivered in a tiny fat bubble called a lipid nanoparticle. Some researchers suspect the immune system’s response to that delivery vehicle is causing the short-term side effects.”

Public needs to prep for vaccine side effects

Still, polyethylene glycol or PEG could cause an allergic reaction.

It is important to remember that polyethylene glycol has been used in vaccines before – to inactive some flu vaccines, but likely only remained in the vaccines in residual amounts.

And know that pegylated medications have been used for some time. For example, pegylated liposomal doxorubicin, which has a polyethylene glycol (PEG) layer around a doxorubicin-containing liposome, has been used since 1995. It has fewer side effects than doxorubicin and the PEG layer doesn’t trigger extra allergic reactions.

“There is no specific ingredient in the [COVID-19] vaccine that would be expected to trigger an allergic reaction.”

Mitchell H. Grayson, MD, FAAAAI.

Mostly, we need to understand that post-authorization safety systems are continuing to monitor these reactions.

“Because of reports of anaphylactic reactions following vaccination outside of clinical trials, the additional following guidance is proposed: A severe allergic reaction to any vaccine or injectable therapy (IM, IV or SC) is a precaution to vaccination at this time; vaccine providers should observe patients after vaccination to monitor for the occurrence of immediate allergic reactions: persons with a history of anaphylaxis (not due to vaccines or injectable medications) 30 minutes, all other persons 15 minutes.”

Messages from the AAAAI COVID-19 Response Task Force

And that even as we see some reports of folks have these reactions in media reports, an awful lot of people have been vaccinated and protected without any problems, except mild and moderate side effects that quickly go away.

And health care providers are standing by to diagnose and treat anyone who does have an allergic reaction after their dose.

Is Anaphylaxis a Contraindication to Getting the COVID-19 Vaccine?

Not surprisingly, anaphylaxis is a contraindication to getting the COVID-19 vaccine.

Until you have been evaluated by an allergist-immunologist, you should not get a COVID-19 vaccine if you have had a severe allergic reaction to any of its components, including polyethylene glycol and polysorbate.
Until you have been evaluated by an allergist-immunologist, you should not get a COVID-19 vaccine if you have had a severe allergic reaction to any of its components, including polyethylene glycol and polysorbate.

But, this contraindication is only if you have had anaphylaxis to one of the components of the COVID-19 vaccine.

If you have a history of allergies unrelated to the components of the COVID-19 vaccine, then you can be vaccinated and protected.
If you have a history of allergies unrelated to the components of the COVID-19 vaccine, then you can be vaccinated and protected.

In most cases, even if you have had anaphylaxis to something else, whether it is peanuts, sulfa drugs, a wasp sting, or even another type of vaccine, then you can still get a COVID-19 vaccine – again, as long as you have never had an anaphylactic reaction to any of the components of the COVID-19 vaccine.

Note that although polysorbate is not an ingredient in either the Pfizer or Moderna COVID-19 vaccines, but according to the CDC, “Polyethylene glycol (PEG), an ingredient in both mRNA COVID-19 vaccines, is structurally related to polysorbate and cross-reactive hypersensitivity between these compounds may occur.”

And since polysorbate is an ingredient in many vaccines, check a list of vaccine excipients if you have had a severe allergic reaction to a vaccine before getting your COVID-19 vaccine.

Also, with a history of anaphylaxis due to something other than a component of the COVID-19 vaccines, after vaccination, you should be observed for 30 minutes.

If you have had a severe allergic reaction to a component of the COVID-19 vaccines, including polysorbate, you either shouldn’t receive the vaccine or you might get evaluated by an allergist-immunologist to see if it would be safe to get vaccinated under observation, in a setting with advanced medical care available.

What to Know About Allergic Reactions to COVID-19 Vaccines

The bottom line is that most people, even those with a history of severe allergies, can still get vaccinated as long as they haven’t had a severe reaction to a component of the COVID-19 vaccines, including PEG and polysorbate.

More on Allergic Reactions to COVID-19 Vaccines

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