Doctor with mask holding a covid-19 vaccine.
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Updated Dec. 17: The Pfizer-BioNTech vaccine has begun to roll out in the fight against the coronavirus pandemic. Emergency use approval for the Moderna vaccine – the other mRNA-based vaccine – is also expected soon in the U.S. and Canada.

In the allergy community, safety questions are arising, after two health-care workers in the U.K. experienced anaphylaxis-like reactions during the British launch of the Pfizer vaccine. Then on Dec. 15, a health-care worker at Barlett Regional Hospital in Juneau, Alaska, similarly had an anaphylactic reaction to the Pfizer vaccine. A second staff member at the hospital also showed symptoms, which resolved quickly. But his reaction (lightheadedness, puffy eyes and scratchy throat) was not viewed as anaphylaxis.

After getting the shot, the first Bartlett Regional employee experienced increased heartbeat, shortness of breath, hives and flushing. The hospital said in a late evening Dec. 16 virtual press conference that her symptoms were consistent with anaphylaxis, and she was treated with epinephrine. The New York Times reports her symptoms subsided but re-emerged, so she was then treated with an epinephrine drip and steroids and treated until early Dec. 16.

The hospital and Alaskan health authorities have reported the incidents to the Center for Disease Control and Prevention’s Vaccine Adverse Event Reporting System (VAERS) database, but have no plans to change the vaccine rollout. A senior CDC official on the press call said the Bartlett Regional response shows the effectiveness of the agency’s recommendations of: 15-minute monitoring patients after the shot, and of having emergency equipment (e.g. epinephrine and oxygen) on hand.

In interviews with Allergic Living, allergists and other experts have stressed the strong safety results in large clinical trials of the two mRNA vaccines. The Pfizer trial involved over 43,000 participants, and saw some side effects but no serious allergic reactions. The experts remind that allergic reactions to vaccines in general are rare. Also to keep the reaction news in context, thousands of people are being immunized with the COVID-19 vaccine during these rollouts.

Dr. Kimberly Blumenthal says to keep in mind that people are allergic to specific triggers. “Allergy to a food doesn’t mean you are allergic to drugs. Allergy to drugs doesn’t mean you are allergic to vaccines,” notes the drug allergy expert at Massachusetts General Hospital.

In this article, Allergic Living recaps what is known so far of any risks or allergy precautions with mRNA vaccines, along with answers to some frequent questions. This post will be updated regularly.   

Background on vaccine authorization

On Dec. 13, the U.S. Centers for Disease Control and Prevention (CDC) approved emergency use authorization (EUA) for the Pfizer mRNA vaccine, for those 16 years of age and older. This followed the FDA’s sanction for the EUA and positive independent expert reviews of the Pfizer vaccine’s clinical trial data. In Britain, the initial rollout started on Dec. 8. On Dec. 9, Canada authorized the Pfizer shot as well.

An independent panel will review the data on the Moderna mRNA vaccine in a public hearing on Dec. 17. It will give the FDA a recommendation on whether to give an EUA to the vaccine. If it is positive, the FDA is likely to give its authorization soon after.

Who Should Not Get the Pfizer mRNA Vaccine?

The FDA worked with Pfizer on the prescribing fact sheet for those receiving the vaccine. It says you should not get the vaccine if you:
• had a severe allergic reaction to any ingredient of this vaccine.
• had a severe allergic reaction after a previous dose of this vaccine. (The vaccine is a two-dose series.)

On the first point, the American College of Allergy, Asthma, and Immunology (ACAAI) released guidance to its allergist members specifying that, based on information to date: “the Pfizer-BioNTech COVID-19 vaccine should not be administered to individuals with a known history of a severe allergic reaction to polyethylene glycol.”

PEG, as it’s called, is a component of the vaccine. However, Dr. Blumenthal says anaphylaxis to PEG has to date been rare. There is also no confirmation of whether it triggered either U.K. reaction.

Can I get the COVID-19 vaccine if I’ve got food allergy, drug allergy, latex allergy or insect allergy?

In its guidance to doctors on the Pfizer vaccine, the CDC says:

1. There is no restriction in the U.S. on receiving the Pfizer COVID-19 vaccine for anyone who has:

• A history of food, pet, insect, venom, environmental or latex allergies.
• A history of allergy to oral medications.
• Non-serious allergy to vaccines or other injectables (e.g. no anaphylaxis).
• Family history of anaphylaxis.
• Immuno-compromising conditions.

A 15-minute observation period is recommended. On the question of those who’ve had anaphylaxis to another vaccine, the CDC’s Dr. Sarah Mbaeyi said in a webinar for doctors:

“People who do report those types of anaphylactic reactions to other vaccines or injectables – they can still get the vaccine, but they should be counseled about the unknown risks of developing a severe allergic reaction and balance these risks against the benefit of vaccination.”  

2. Caution should be used when considering vaccination for:
• People with moderate-to-severe illness who have a history of anaphylaxis to another vaccine or a history of anaphylaxis to an injectable medication.

If a doctor and patient decide to go ahead with the inoculation in this case, the CDC recommends a 30-minute observation period.

Ingredients of the Two mRNA Vaccines

The FDA’s briefing document for its advisory committee that reviewed the Pfizer BioNTech COVID-19 vaccine lists the following ingredients:

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-snglycero-3-phosphocholine, and cholesterol), potassium chloride, monobasic potassium phosphate, sodium chloride, dibasic sodium phosphate dihydrate, and sucrose.

The FDA’s briefing document for its advisory committee that will review the Moderna COVID-19 vaccine lists the following ingredients:

The Moderna COVID-19 Vaccine is a white to off-white, sterile, preservative-free frozen suspension for intramuscular injection. The vaccine contains a synthetic messenger ribonucleic acid (mRNA) encoding the pre-fusion stabilized spike glycoprotein (S) of SARS-CoV-2 virus. The vaccine also contains the following ingredients: lipids (SM-102, 1,2-dimyristoyl-rac-glycero3-methoxypolyethylene glycol-2000 [PEG2000-DMG], cholesterol, and 1,2-distearoyl-snglycero-3-phosphocholine [DSPC]), tromethamine, tromethamine hydrochloride, acetic acid, sodium acetate, and sucrose.

The lipids (or fats) in the ingredients serve as a slippery coating that helps to slide the vaccine into the cells. Neither vaccine contains food proteins.

PEG is a component of the mRNA vaccines. Is that safe for people with soy allergy?

Polyethylene glycol or PEG is used to coat and protect the mRNA vaccine. We put the soy allergy question to two experts: allergist and vaccine expert Dr. James Baker, director of the Mary H. Weiser Food Allergy Center at the University of Michigan, and Dr. Kimberly Blumenthal, allergist and the safety officer for allergy at Massachusetts General Hospital. Both say there is no soy protein or other food protein in the mRNA vaccines. 

“The PEG component of these vaccines are derivatives of soy sterols (lipids) that are not cross-reactive with soy proteins that cause soy allergy,” stresses Dr. Baker.

Dr. Blumenthal agrees, telling Allergic Living: “Soy allergy is from protein, never plant-derived fatty acids” (the ‘lipids’ that Dr. Baker references). Importantly, she adds as a drug allergy expert: “Soy-allergic patients tolerate PEG all the time.”

In rare cases, PEG can trigger allergic reactions. However, Dr. Baker notes: “PEG derivatives that cause allergies usually involve some different protein. For example, PEG-asparaginase, an anti-cancer drug, which is altered by complexing with PEG. There is no cross-reaction between soy allergy and allergy to other PEG-conjugated proteins.”

Are the mRNA vaccines safe for people with egg allergy?

“There is no egg or egg-related component of the RNA vaccines,” says Dr. Baker. “Therefore, these vaccines are totally safe for egg-allergic individuals. While we do not know what caused the reaction seen in the one patient in Great Britain [who has a history of food allergy], it is definitely not allergy to egg.”

This question likely arises in part because of common misunderstanding about egg allergy in relation to the flu shot and the MMR vaccine. In both those cases, health authorities have investigated and recommend that these vaccines are safe and effective for those with egg allergy. For the flu shot see this link for the MMR see this link.

Are the mRNA vaccines safe for people with celiac disease?

A group of leading North American celiac experts with the Society for the Study of Celiac Disease (SSCD) answers this question:

“As the safety and efficacy data on COVID vaccination has emerged, there is no evidence to suggest that people with celiac disease would be more prone to an adverse effect of vaccination. Celiac disease is not considered an allergy, and by itself does not prompt additional precaution when proceeding with vaccination. Patients with concerns about vaccination and their particular circumstance should speak with their health care provider.”

What exactly is an mRNA vaccine?

In large clinical trials, the mRNA vaccines proved highly effective in preventing the coronavirus. The Pfizer shot had 95% efficacy in its study, while the Moderna vaccine had an efficacy rate of 94.1%. But how do these novel therapies work with the immune system?

To trigger an immune response, many vaccines put a weakened or inactivated germ into our bodies. But mRNA vaccines work differently. The CDC explains that these vaccines instead “teach our cells how to make a protein – or even just a piece of a protein – that triggers an immune response.” This leads the immune system to produce antibodies against the virus, which will protect an inoculated person who is exposed to the real virus.

When a COVID-19 mRNA vaccine is injected into the arm muscle, the CDC explains that the mRNA gives “instructions for our cells to make a harmless piece of what is called the ‘spike protein.’ The spike protein is found on the surface of the virus that causes COVID-19.”

After the protein piece is made, the CDC says a cell will destroy the genetic material from the vaccine. Next, when cells display the protein, “our immune systems will recognize that the protein doesn’t belong there and begin building an immune response and making antibodies, like what happens in natural infection against COVID-19.”

A few weeks after vaccination, the body is left with a supply of white blood cells – “memory” T-lymphocytes as well as B-lymphocytes – that will know to fight the virus.  

Allergist Dr. David Stukus, an associate professor of pediatrics at Nationwide Children’s Hospital, explained in an Instagram Q&A that “the mRNA part is just a blueprint, it’s harmless.” After we inject it into our bodies and the spike protein is built, “our immune systems, which are so robust, recognize that foreign antigen. Then if we encounter the spike protein in real life, our immune system says, ‘Hey, you don’t belong here,’ and we can mount a very rapid and protective antibody response.”

During clinical trials for the mRNA vaccines, what adverse reactions were seen? 

In Pfizer’s clinical trial of over 43,000 study participants who received either the vaccine or its placebo, data show some side effects. These include injection site pain, fatigue, headache, muscle or joint pain, chills or vomiting. The data further show a small number of suspected allergic reactions in both the vaccine and placebo groups, but at a rate of less than 1% (0.63% and 0.51% respectively).

The FDA conducted an independent analysis of Pfizer’s clinical trial results, and found a few instances of potential minor allergic reactions among participants. None were considered serious or required epinephrine.

In an FDA review of Moderna’s Phase 3 trial of just over 30,000 people who received two shots of either the vaccine or placebo, side effects included injection site pain, fatigue, headache, muscle or joint pain and chills.  

Bell’s Palsy fact-check: During the Pfizer trial, four cases of Bell’s palsy (temporary facial paralysis) emerged in the treatment group and there were four cases in the Moderna trial (three in the treatment group and one with a placebo patient).

The FDA says this may or may not relate to mRNA vaccination, and will continue to be monitored. The incidence for Bell’s palsy within 43,000 people involved in the Pfizer trial was actually lower than the normal incidence rate in the general population. In its report on the Pfizer vaccine, the FDA writes:

“The observed frequency of reported Bell’s palsy in the vaccine group is consistent with the expected background rate in the general population, and there is no clear basis upon which to conclude a causal relationship at this time, but FDA will recommend surveillance for cases of Bell’s palsy with deployment of the vaccine into larger populations.”

What happened to the 2 healthcare workers in England who reacted?

The U.K. health authorities are reviewing these two cases, which were reported on Dec. 9. Little information has been made public yet. What’s known is that two women in their forties, who are healthcare workers, had what have been described by officials as either “anaphylactic” or “anaphylactoid” reactions to the vaccine. (The latter are reactions that bring on mast cell or basophil degranulation but don’t involve IgE allergy antibodies.) There is also a third U.K. case that is called a “possible allergic reaction.”

Patrick Caubel, Pfizer’s head of safety, told the FDA’s reviewing panel:
– One woman has food allergies and reported in past having anaphylaxis that required epinephrine.
– The second has a history of an allergic reaction to one or more medications, “although we don’t know which drugs yet.”
– The second woman experienced shortness of breath but her reaction was “more minor,” he said. Both women were treated and recovered.

The FDA completed an independent analysis of Pfizer’s clinical trial results, and found a few instances of what could potentially have been minor allergic reactions among trial participants. An FDA official said none required the use of an epinephrine injection. 

Who was excluded from the Pfizer trial?

Contrary to some early reports, Pfizer told the FDA reviewing panel of experts that people with a history of severe food or drug allergies were not excluded from the vaccine’s Phase 3 trial.

So who was excluded? Those who had a past severe adverse reaction to any vaccine or to a component of this vaccine, said Pfizer’s senior vice president of vaccine clinical research and development.

Allergist Dr. David Stukus noted in our Instagram discussion that clinical trials have strict inclusion and exclusion criteria. In research, “you’re trying to control for all confounding variables that you can. If you enroll someone who’s had anaphylaxis to a prior vaccine and then they have anaphylaxis to this vaccine, it just clouds all the data.” Stukus also stressed that “true anaphylaxis to any vaccine is exceptionally rare, it’s 1 in a million across the board.”

Should I get vaccinated if I’m pregnant or breastfeeding?

The CDC says there are no data on the safety of COVID-19 vaccines in pregnant women, since they were not included in the clinical study.

The American Academy of Pediatrics (AAP) notes that the CDC vaccine review committee recommends pregnant women “discuss the risks and benefits of being vaccinated with their healthcare provider.”

AAP quotes CDC medical officer Dr. Sarah Mbaeyi’s advice: “Pregnant women and healthcare providers should consider the level of COVID-19 community transmission, her personal risk of contracting COVID-19, the risks of COVID-19 to her and potential risk to the fetus, the efficacy of vaccine, side effects of the vaccine, and the lack of data about vaccine use during pregnancy.” See the CDC briefing for more details here.

Plus, the American College of Obstetricians and Gynecologists (ACOG) offers its recommendations for pregnancy and the vaccine here.

The AAP says a pregnant woman who gets a fever following vaccination should take acetaminophen, since fever “is associated with adverse pregnancy outcomes.” 

The CDC committee noted that because it is not a live-virus vaccine, it is not considered a risk to a breastfeeding infant. But again, consult your physician.

If you get an mRNA vaccine…

The CDC asks you to register with V-safe, its smartphone monitoring program. It uses text messaging and web surveys to follow-up with vaccine recipients. Should you have any adverse side effects, V-safe lets you to report them to assist in data gathering awareness. 

For adverse effects of significance, the CDC says a representative will get in touch.

Related Reading:
As FDA Approves COVID-19 Vaccine, Experts Seek to Calm Allergy Fears
Instagram Live with Dr. David Stukus and Editor Gwen Smith
CDC’s FAQ of General COVID-19 Vaccination Questions
AAP Summary of CDC Advice


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