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What Physicians Should Know About COVID-19 Vaccine Allergy: Q&A with Kimberly Blumenthal, MD, MSc

In This Article

  • Since the mRNA COVID-19 vaccine rollouts in the U.S. and the U.K., rare cases of severe allergy have been reported to the CDC, causing concern in the media about allergic reactions related to the new vaccine
  • This is the first time mRNA vaccines have been approved for use in humans and much is still to be learned
  • In this Q&A, Kimberly Blumenthal, MD, MSc, discusses what may cause an allergic reaction to the vaccine, what makes someone higher risk for an adverse event and what doctors can do to help patients understand and manage the risk

Two mRNA-based SARS-CoV-2 vaccines by Pfizer and Moderna received emergency use authorization from the FDA in December 2020. Since the Pfizer vaccine rollout in the U.S. and the U.K., more than a dozen cases of severe allergy have been reported to the CDC, causing concern in the media about allergic reactions related to the new vaccine. Reactions have also been reported to the Moderna vaccine. In this Q&A, Kimberly Blumenthal, MD, MSc, Quality and Safety officer for Allergy and co-director of the Clinical Epidemiology Program in the Division of Rheumatology, Allergy and Immunology at Massachusetts General Hospital, discusses potential causes of COVID-19 vaccine allergy, what makes someone higher risk for an adverse event and what doctors can do to help patients understand and manage the risk.

Q: Why is there concern about allergic reactions to the COVID-19 Vaccine?

Blumenthal: We have some concern right now because although there wasn't a signal in the clinical trials related to allergic reactions to the COVID-19 vaccines, we've since seen cases of allergy—first in the United Kingdom and now in the United States. Some of the reactions were severe and consistent with anaphylaxis. This is a signal that we wouldn't anticipate from what we know about vaccine allergy generally, or what we know about this vaccine and its ingredients.

In the big picture, usually, about one person in a million has a vaccine allergy. The data so far suggest that something may be a little bit different here.

Q: What may be causing these reactions to vaccines? Are there specific allergies that people have that may make them more susceptible to allergic reactions to the vaccine?

Blumenthal: We don't know what's causing this yet or even if there are multiple causes or mechanisms. This could be allergy in the traditional sense, caused by IgE antibodies or the reactions could be from another process. Some symptoms experienced after vaccination may also turn out to be something else entirely, like a vasovagal reaction or even anxiety. We still don't know all of the potential factors at play.

There are a lot of confusing messages around whether patients with allergies need to be worried about this vaccine. This vaccine does not have any food allergens. It doesn't have any latex. It does not have the ingredients of any other drug that we've seen.

If you have an allergy to penicillin, for example, there's no reason why you would have a problem with this vaccine.

The FDA and the CDC put forth guidance that suggests a longer observation after vaccination of 30 minutes for patients who have had anaphylaxis in the past. There is also additional guidance for patients who have had anaphylaxis to an injectable medication or vaccine that these patients have a clinical assessment prior to vaccination. Finally, patients with an allergic reaction to this vaccine or its ingredients should not be vaccinated with the Pfizer or Moderna vaccines according to the FDA guidance.

It is possible that people with severe allergy histories may be a little bit higher risk than the clinical trial population that did not include people with severe allergies to vaccines.

The concern about an allergy history to an injectable medication or to a vaccine in the past is related to an inactive ingredient in the Pfizer and Moderna vaccines called polyethylene glycol (PEG). People are very rarely allergic to PEG. It's relatively easy for someone to confirm that they can tolerate PEG because it's everywhere. It is in the medications we have taken for colonoscopies and in steroid injections for arthritis, for example.

We also are learning about whether another inactive ingredient, polysorbate, might also warrant attention because it is the inactive ingredient in the Astra Zeneca and Johnson and Johnson vaccines. I just queried Mass General Brigham system, and there are only about 300 people out of 1.2 million who have allergies to PEG or polysorbate, and only a small portion of those have an allergy that might be considered severe.

So, the take-home message is that most patients don't need to worry at all about allergy.

Q: Which patients should not get the COVID-19 vaccine?

Blumenthal: From an allergy perspective, the only people who cannot get the shot are people who have an allergic reaction after having this shot or those patients who have a severe allergy to a component of the shot (PEG). So likely just a few hundred people across Mass General Brigham system cannot get it right now without allergy input—and maybe testing—first.

Q: How should medical professionals evaluate whether there is an allergy concern for a patient?

Blumenthal: The patient's allergy history is so important here. It's so important that even for our employee program, we're setting up virtual visits. We can talk with them about what the symptoms and signs of allergy are with the patient and get to know their history—we don't need to do an allergy test necessarily.

Now we're developing some skin testing tools that'll be helpful for that small group of people we think might have an additive allergy. But it's mostly just talking about what their history is and trying to get a sense of what the actual allergy was.

Q: How should medical professionals prepare for potential allergic reactions?

Blumenthal: In our clinical practice we often monitor people who are at risk of anaphylaxis for 30 (typical for allergy shots) to 60 minutes (typical to prove a penicillin allergy is outgrown). For this vaccine, the CDC recommends observing most patients for 15 minutes after vaccination, but 30 minutes for patients with a history of severe allergic reactions. This is a precaution to monitor for immediate reactions. This may be the most important guidance to ensure the safety of patients.

Next, my recommendation aligns with the most recent CDC guidance that ensures that every place that administers this vaccine can diagnose and treat anaphylaxis quickly. This includes equipment to take vital signs and medication availability. The number one medication for anaphylaxis is epinephrine, and that is most reliably administered in an autoinjector such as an epi-pen. And then there are other medications you might think about after you have addressed anaphylaxis, such as antihistamine if there's a lot of itching.

Then having a known process for where a patient goes if they have a reaction and are given epinephrine. Do they go to an Emergency Department? Urgent care? For example, if a vaccine clinic is in remote areas, knowing where to refer the patient immediately is important.

And then diagnostically figuring out what is going on mechanistically is critical. We are going to need blood work and follow up testing on any patients with possible anaphylaxis. We need to find out what they're reacting to gain knowledge to apply to future mRNA vaccine administration.

Q: Are you conducting any research on COVID-19 vaccine allergies?

Blumenthal: Right now, I'm doing Department of Medicine funded research on our employee vaccination program. We have IRB approval and follow employees through their vaccination to answer the questions about the how often this happens in our setting and whether allergy poses a risk. We were able to set up a robust clinical program in a matter of weeks and we're actively vaccinating our employees (about 20,000 to date). At Mass General Brigham, we have more allergists interested in drug allergy than anywhere else in the country and I think we're set up to study this as best as anyone else. We also anticipate our health care system will be involved with the large study being planned by NIAID.

Q: Are there any resources for clinicians to learn more or ask questions about COVID-19 vaccine allergy?

Blumenthal: In allergy, we have two United States professional organizations that have been very good with releasing guidance and answering allergy specific questions. That's the American Academy of Allergy, Asthma & Immunology and American College of Allergy, Asthma and Immunology. And they've both been releasing updates, guidance and very practical advice that goes beyond allergy specialist use because the primary care doctors will be answering most of these questions across America. There are only 5,000 allergists in the U.S.—there's not a lot of allergists. Therefore, a lot of people with severe food, medication, steroid or vaccine allergy are going to be addressing this with their primary care doctor.

The CDC guidance and materials on allergy have been regularly updated since the EUAs for the vaccines and are also a great resource for the basics.

Q: What do you say to anyone concerned about getting the COVID-19 vaccine?

Blumenthal: I would say that it is important to weigh the risk of anaphylaxis (and its potential harm) versus the risk of getting the disease (and its potential harm). Even if I were in the highest risk allergy group, I would still get in line to get the vaccine. I might want to be vaccinated closer to an academic medical center or somewhere where I can get a high level of care, if needed.

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Learn more about the Division of Rheumatology, Allergy and Immunology at Mass General

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