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This has been reviewed and updated as of January 17, 2021.
Nearly as soon as the mRNA COVID-19 vaccines from Pfizer and Moderna were granted emergency use authorization in the United States and started rolling out in other countries around the world, questions arose about their link with allergic reactions in some recipients, including anaphylactic (very serious and even life-threatening) reactions.
You may be wondering if you should get the vaccine if you have a history of severe allergic reactions.
How Common Are Allergic Reactions, Including Anaphylaxis, to the COVID-19 Vaccine?
The answer is reassuring so far: Allergic reactions are not common and anaphylactic reactions are very rare.
The CDC recently published a report of the data they gathered from people who received a Pfizer COVID-19 vaccine between December 14 and 23, 2020. There were 21 cases of anaphylaxis and 83 cases of non-anaphylaxis allergic reaction after administration of 1,893,360 first doses of the Pfizer COVID-19 vaccine.
- 86% of anaphylaxis cases had symptom onset within 30 minutes of vaccination
- 81% anaphylaxis cases of had a history of allergies or allergic reactions, including some with previous anaphylaxis events
- 90% of anaphylaxis cases were treated with epinephrine as part of therapy and no deaths have been reported
- 87% of non-anaphylactic cases were classified as nonserious
- 85% of non-anaphylactic cases had a symptom onset within 30 minutes of vaccination
- 67% non-anaphylactic cases had a past history of allergies or allergic reactions
Why Can the COVID-19 Vaccine Cause an Allergic Reaction?
Despite the reports of allergic reactions occurring after administration of the Pfizer and Moderna COVID-19 vaccines, officials haven’t pinpointed a specific ingredient or connection between the vaccine and the reported reactions.
Both the Pfizer and Moderna vaccines contain a short list of ingredients, one of which is a molecule called messenger RNA that degrades within about a day of being injected and is unlikely to be a threat. The other ingredients are a mix of fatty substances, salts, and sugars that stabilize the vaccine, but none are common allergens.
That said, experts have eyed polyethylene glycol, which is the only chemical in the vaccine known to cause allergic reactions (although rarely). Polyethylene glycol is found in laxatives and bowel preps for colonoscopies and is also sometimes used as a stabilizer in vaccines.
The American College of Allergy, Asthma, and Immunology (ACAAI) has also warned about issues for people with a history of allergies to polysorbate or polyoxyl 35 castor oil (e.g. paclitaxel), because these may cross-react with PEG.
As the vaccine continues to be administered, more research will be needed to determine what exactly causes allergic reactions.
The Moderna vaccine utilizes a different blend of lipids in its vaccine than the Pfizer vaccine does, which makes it more stable. That’s why it doesn’t need to be refrigerated at extremely cold temperatures like the Pfizer vaccine, according to Your Local Epidemiologist. Because of that, it’s not known whether both vaccines could cause similar rates of allergic reactions and should be studied separately as they roll out. Like the Pfizer vaccine, the Moderna vaccine also includes polyethylene glycol.
Can You Get a COVID-19 Vaccine If You’ve Have a History of Allergic Reactions?
The short answer is: probably, but with caution. Here’s the latest information, based on the type of allergic reactions you’ve had in the past.
If You’ve Had an Allergic Reaction to a Previous COVID-19 Vaccine or Its Ingredients
The current guidance from the U.S. Centers for Disease Control and Prevention says that people who meet the following criteria should not get either the Pfizer or Moderna COVID-19 vaccine at this time:
- You’ve had a severe allergic reaction (anaphylaxis) after a previous dose of an mRNA COVID-19 vaccine or any of its components
- You’ve had an immediate allergic reaction of any severity to a previous dose of an mRNA COVID-19 vaccine or any of its components (including polyethylene glycol [PEG])*
- You’ve had an immediate allergic reaction of any severity to polysorbate (due to potential cross-reactive hypersensitivity with the vaccine ingredient PEG)*
* The CDC says these groups should not receive an mRNA COVID-19 vaccine at this time unless they have been evaluated by an allergist-immunologist and it is determined that the person can safely receive the vaccine (such as under observation, in a setting with advanced medical care available).
Ingredients in the Pfizer and Moderna COVID-19 Vaccines
Here are the ingredients in the Pfizer-BioNTech vaccine, according to the fact sheet from the U.S. Food and Drug Administration (FDA).
- 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
Here are the ingredients in the Moderna vaccine, according to the fact sheet from the U.S. Food and Drug Administration (FDA).
- Messenger ribonucleic acid (mRNA)
- Lipids (SM-102, polyethylene glycol [PEG] 2000 dimyristoyl glycerol [DMG], cholesterol, and 1,2-distearoyl-sn-glycero-3-phosphocholine [DSPC])
- Tromethamine hydrochloride
- Acetic acid
- Sodium acetate
If You Have a History of Allergic Reactions to Other Vaccines or Infused or Injectable Medication
If you’ve had an immediate allergic reaction to an infused or injectable medication — such as a biologic for an inflammatory or autoimmune disease — the CDC says you should consider it as a precaution and discuss it with your doctor before getting either the Pfizer or Moderna COVID-19 vaccine. The CDC says you “should be counseled about the unknown risks of developing a severe allergic reaction and balance these risks against the benefits of vaccination.”
The American College of Allergy, Asthma & Immunology (ACAAI) says to consider these questions:
- Do you have a history of severe allergic reaction to an injectable medication (intravenous, intramuscular, or subcutaneous)?
- Do you have a history of a severe allergic reaction to a prior vaccine?
- Do you have a history of a severe allergic reaction to polyethylene glycol (PEG), a polysorbate or polyoxyl 35 castor oil (e.g. paclitaxel) containing injectable or vaccine?
The ACAAI states that if you answer yes to any of these questions, you should speak to a board-certified allergy and asthma doctor before getting the vaccine.
The reason the experts are recommending caution for people with a history of allergic reactions to infused or injectable medications is that some may contain ingredients, like polysorbate, that can cross-react with the polyethylene glycol [PEG] in the COVID-19 vaccine.
However, remember that the CDC is NOT saying that all people who have had allergic reactions to infused or injectable medications should not get a COVID-19 vaccine — just that it’s a good idea to speak with your doctor to review your medical history and make sure it’s safe to get the vaccine.
Keep in mind that there’s a difference between having an allergic reaction to an infused or injectable medication vs. a side effect of the medication.
“We need to determine if a patient has had an anaphylactic reaction to an infused or injected medication. They should likely avoid COVID-19 vaccines for now. For people with milder reactions, it is more of a risk versus benefit decision-making process,” says Nilanjana Bose, MD, a board-certified rheumatologist with the Rheumatology Center of Houston.
If you’re not sure whether your side effects after receiving an infused or injected medication are considered an allergic reaction, ask your doctor.
Read more here about what to know if you have a history of allergies to infused or injectable medications.
If You Have a History of Allergic Reactions to Food, Pets, or Other Environmental Triggers
The CDC says that a history of allergic reactions, even severe reactions, to food, pets, venom, latex, eggs or gelatin, or other environmental triggers is not a contraindication to getting a COVID-19 vaccine.
This means you can get a COVID-19 vaccine if you have a history of allergies to these things, although of course you should ask your doctor if you have any specific concerns or questions.
“Individuals with common allergies like those to foods, medications, environmental factors, venom, and latex are no more likely to have an anaphylactic reaction than the general public,” says Robyn J. Kreiner, MD, a board-certified allergist and immunologist at Strauss Allergy & Asthma in Long Island, New York.
Should Everyone Be Monitored After Receiving the COVID-19 Vaccine?
Yes — whether or not you have had allergic reactions in the past. The CDC states that you should be observed for 15 minutes by your vaccine provider to make sure you don’t have an adverse reaction.
Those who have a history of anaphylaxis due to any cause need to be monitored for 30 minutes after vaccination. You should also be monitored for 30 minutes if there are any concerns about your being at increased risk of having an allergic reaction.
Recognizing Allergic Reactions to a COVID-19 Vaccine
It’s important to distinguish side effects from the vaccine with allergic reactions to it. Most people who get the vaccine experience some common side effects. These include pain at the injection site, fatigue, headache, muscle pain, chills, joint pain, and fever, and typically last several days.
“The common side effects of these vaccines are very common to other vaccines,” says Dr. Kreiner. “And like other vaccines, the symptoms do self-resolve.”
Allergic reactions to the COVID-19 vaccine would generally fall into one of two categories: non-severe immediate reactions and severe reactions, per the CDC.
Non-severe reactions that occur within four hours of getting vaccinated are known as immediate allergic reactions. Symptoms include:
Severe allergic reactions require treatment with epinephrine or an EpiPen, or treatment at a hospital, according to the CDC. This is also known as anaphylaxis. Symptoms include:
- Low blood pressure
- Constriction of airways
- Wheezing (respiratory distress)
- Swollen tongue or throat
- A weak and rapid pulse
- Nausea, vomiting, or diarrhea
- Loss of consciousness
Is a COVID-19 Vaccine Riskier Than Other Kinds of Vaccines?
In general, severe allergic reactions to vaccines are very rare — with influenza vaccines, anaphylaxis has been reported at a rate of one in 1 million or less, per Vanderbilt University Medical Center.
In the CDC’s report of people who received the Pfizer vaccine, the rate of anaphylaxis was slightly higher: 21 cases of anaphylaxis among 1,893,360 vaccine doses is about 11 cases per million doses.
That said, it’s too early to draw any major conclusions or comparisons. In its analysis of initial data, the CDC warned that it’s possible that “intense media attention around the national COVID-19 vaccination program and heightened awareness of reports of anaphylaxis have affected vaccine recipient and health care provider behavior and practices, including elevated concern and anxiety, higher index of suspicion for anaphylaxis, and lower threshold for early treatment of suspected cases, thereby resulting in an increase in diagnosis of suspected anaphylaxis.”
Another potential bias might be that there’s a lag in reporting the total number of vaccine doses administered (the “denominator”), which could make it appear that the rate of anaphylaxis cases (the “numerator”) is higher than it actually is.
The CDC’s report concludes with this important statement: “Mortality [death] from COVID-19 in populations at high risk is substantial and treatment options are limited. Widespread vaccination against COVID-19 with highly effective vaccines represents an important tool in efforts to control the pandemic. CDC and FDA will continue to monitor for adverse events, including anaphylaxis, after receipt of COVID-19 vaccines and will regularly assess the benefits and risks of vaccination.”
The Importance of Getting the COVID-19 Vaccine
As of now, the criteria for people who should not get a COVID-19 vaccine is very narrow. The CDC is saying that people who have had a severe allergic reaction to a previous dose of a COVID-19 vaccine should not receive another dose, for now.
But for everyone else — including people who had non-anaphylactic allergic reactions to a COVID-19 vaccine, people who have allergies to ingredients in the COVID-19 vaccine, and people who have had allergic reactions to infused or injectable medications — the vaccine may be given, but it’s important to discuss this with your doctor and make sure the vaccine can be given in a safe environment. This means making sure the person can be observed for 30 minutes afterward and medical care is available.
It may seem concerning that some people have had allergic reactions to the vaccine, but keep in mind that the number of reactions is very small in comparison to the total amount of vaccines administered.
And most important: “The overall statement that people should be aware of is that the benefits of getting the COVID-19 vaccine far outweigh the risks of the possible chance of an anaphylactic reaction to the vaccine,” says Dr. Kreiner.
If you’re worried about potential allergic reactions to the COVID-19 vaccine once it becomes available to you, the best course of action is to speak to your doctor about any previous allergic reactions you’ve had.
Your physician can then compare what you’ve had prior reactions to with the list of ingredients in the Pfizer-BioNTech COVID-19 vaccine or Moderna COVID-19 vaccine.
“If it’s the case that there’s no connection between those, then I think you’re probably going to be okay to get the vaccination,” says infectious disease physician Amesh A. Adalja, MD, a Senior Scholar at Johns Hopkins Center for Health Security. “If there is a connection, then you have to think about the risks and benefits of getting the vaccine, and wait around for 30 minutes afterward to make sure you don’t have a reaction.”
What If You’re Immunocompromised?
The Pfizer and Moderna COVID-19 vaccines are not live vaccines, and they can be given to immunocompromised patients.
However, talk to your doctor about what this means for your COVID-19 mitigation efforts moving forward. There’s a possibility of a diminished immune response to the vaccine in immunocompromised patients, and experts still don’t know how those with weakened immune systems will respond to the vaccine.
“It’s still recommended that immunocompromised patients get this vaccine,” says Dr. Kreiner. “If they were to be exposed to COVID-19, they may not fight it as quickly or efficiently as someone who is not immunocompromised, but they would still have the proper antibodies to attack the spike protein that has been provided by the vaccine.”
If you’re immunocompromised, you should inform your vaccination provider. In fact, before you get the Pfizer-BioNTech or Moderna COVID-19 vaccine, the FDA says you should tell your vaccination provider about all of your medical conditions, including if you:
- are immunocompromised or taking medicine that affects your immune system
- have any allergies
- have a fever
- have a bleeding disorder or are on a blood thinner
- are pregnant or plan to become pregnant
- are breastfeeding
- have received another COVID-19 vaccine
Despite the small risk of allergic reactions, it is especially important to talk to your doctor about getting the vaccine if you’re immunocompromised.
“Immunocompromised individuals may have to consider themselves at higher risk for severe COVID-19, and this vaccine is one way to mitigate that risk,” says Dr. Adalja. “Because of that, I think that the risk-benefit ratio favors the use of this vaccine even more so in immunocompromised individuals than in the general population.”
Also keep in mind that we’re still learning about the long-term effects of COVID-19, but if you stay on site after your vaccination is given, allergic reactions can be treated.
“Anaphylaxis is very treatable, but we don’t have a standard treatment for COVID-19 and there are many new symptoms patients are manifesting that we still are figuring out,” says Dr. Kreiner.
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CDC COVID-19 Response Team; Food and Drug Administration. Allergic Reactions Including Anaphylaxis After Receipt of the First Dose of Pfizer-BioNTech COVID-19 Vaccine — United States, December 14–23, 2020. Morbidity and Mortality Weekly Report. January 15, 2021. doi: http://dx.doi.org/10.15585/mmwr.mm7002e1.
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Interview with Amesh A. Adalja, MD, an infectious disease physician and senior scholar at Johns Hopkins Center for Health Security
Interview with Robyn J. Kreiner, MD, a board-certified allergist and immunologist at Strauss Allergy & Asthma in Long Island, New York
Interview with Nilanjana Bose, MD, a board-certified rheumatologist with the Rheumatology Center of Houston
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