Infectious Disease

Allergic reactions to COVID-19 vaccines are uncommon, however “a lot uncertainty” stays

March 03, 2021

5 min read

Source / information


Kelso J, et al. Allergic Reactions to COVID-19 Vaccines: Distinguishing Between Fact and Fiction. Presented at: American Academy of Allergy, Asthma and Immunology Annual Meeting; February 26 – March 1, 2021 (virtual meeting).

Greenhawt reports that he is a member of the Joint Task Force on Allergy Practice Parameters. Kelso does not report any relevant financial information.


Receive an email when new articles are published

Please enter your email address to receive an email when new articles are published . “data-action =” subscribe “> subscribe

We could not process your request. Please try again later. If you continue to have this problem, please contact [email protected].

Back to Healio

A panel of experts at the American Academy of Allergy, Asthma and Immunology annual virtual meeting highlighted recent findings on allergic reactions to available COVID-19 vaccines and how to assess patients with a reaction.

“In the clinical studies with [the messenger RNA] No anaphylactic reactions have been reported with vaccines involving tens of thousands of patients, but some anaphylactic reactions were reported on the first day they were used clinically in the UK, “said Dr. John Kelso, a practicing allergist in the Department of Allergy, Asthma, and Immunology at Scripps Clinic and volunteer clinical professor of health sciences at the University of California’s San Diego School of Medicine, said during his talk. “Now we’ve been in this range for a few months and the rate of so-called anaphylactic reactions is on the order of 2.5 to 10 per million, the latest estimate is actually 5 per million. So still very rarely. “

Source: Adobe Stock.

The CDC recently released data from the Vaccine Adverse Reporting System (VAERS) for the first month of monitoring COVID-19 vaccine safety in the United States. From December 14, 2020 to January 13, 13,794,904 doses of the Pfizer-BioNTech and Moderna COVID-19 vaccines were administered, and VAERS received and processed 6,994 post-vaccination adverse event reports, including 6,394 (90.8%), who were classified as not serious and 640 (9.2%) as serious. 62 reports of anaphylaxis were confirmed: 46 (74.2%) after receiving the Pfizer BioNTech vaccine and 16 (25.8%) after receiving the Moderna vaccine, according to data published in the Weekly Morbidity and Mortality Report.

The authors of the MMWR report concluded that “[t]These initial results should reassure health care providers and vaccine recipients and build confidence in the safety of COVID-19 vaccines. “

Types of reactions reported

Kelso discussed reactions that have been reported to date that have been characterized as anaphylactic, such as the development of an erythematous rash, feeling of throat blocked, shortness of breath, wheezing, and swelling of the lips or tongue.

“There [is] A range of symptoms that are usually reported within minutes of receiving these vaccines that have been identified as potentially allergic, ”Kelso said.

Kelso said it was important to remember that other reactions might mimic anaphylaxis.

“So, something that can happen to a patient within minutes of receiving a vaccine … [but] That doesn’t necessarily mean it’s an anaphylactic reaction, ”he said. “Vasovagal reactions can also cause drowsiness or even syncope, but are typically preceded by bradycardia and paleness, as opposed to tachycardia and flushing that can occur with anaphylaxis. Vocal cord spasms can certainly cause stridor and dyspnea. Most often, panic attacks, or even just anxiety, can make you feel like a globe … palpitations, shortness of breath, and other symptoms. “

In clinical practice, Kelso recommended the following:

  • Encourage colleagues who oversee vaccination clinics to find out what really happened.
  • Note that there may be a differential diagnosis.
  • Record vital signs and physical exam results from patients with allergic reactions, including the skin, throat, and lungs.
  • In ED or emergency care, draw a mast cell tryptase within hours of possible reactions.
  • Encourage colleagues to refer patients with reactions to COVID-19 vaccines seen in allergy clinics.

The CDC recommends that messenger RNA (mRNA) vaccines should not be given to anyone who has a history of allergic reactions to any of the vaccine components, particularly polyethylene glycol (PEG), as this component is known to cause anaphylaxis. PEG is widely used in medicines, colon supplements, laxatives, cosmetics, and foods. Given these other possible exposures, this could explain how some patients might become sensitized to PEG before receiving a COVID-19 vaccine, but this is just a theory, according to Kelso.

“Even with … the rare patient with PEG allergy, we still don’t know if the vaccine contains enough PEG to actually trigger a reaction. And most importantly, there haven’t been any confirmed cases of anyone having an anaphylactic reaction to the vaccine [and] a positive vaccine skin test and … it was found that PEG is the real allergen, ”said Kelso. “So certainly possible, but remains speculation to this day.”

Joint decisions about vaccinations are key

Joint decisions are critical to vaccinating those at risk, as well as re-vaccinating those who have had allergic reactions to a COVID-19 vaccine.

“Globally, vaccinations are now contraindicated for anyone who has had a history of reacting to any of its components, and additional doses are contraindicated if you had a difficult reaction to the first dose,” said Matthew Greenhawt, MD, MBA, MSc, Associate Professor for Pediatrics in the Department of Allergy / Immunology at Colorado Children’s Hospital and the University of Colorado Medical School and co-director of the Colorado Food Challenge Unit at Aurora, Colorado Children’s Hospital, said during his presentation. “So the question here is whether we should vaccinate or re-vaccinate someone who has had a potential reaction to either the excipient or the initial vaccine dose in the past.”

According to Greenhawt, “we have a lot of uncertainty.”

The CDC’s most frequent update recommends that patients with a history of anaphylaxis unrelated to mRNA vaccines continue to receive a COVID-19 vaccine and be observed for 15 minutes instead of the standard 15 minutes after injection. Individuals with a history of immediate reaction to other drugs that may contain PEG should be referred to an allergist and vaccinated with a 30 minute observation period. and those who have had a severe allergic reaction to an mRNA vaccine should be referred to an allergic immunologist before deciding to vaccinate.

There have been cases where patients may have had allergic reactions to their first dose of COVID-19 vaccine and tolerated a second dose with no more allergic events reported, according to Kelso. However, performing a second dose must involve mutual decision-making.

“Whether people have a reason not to believe they even wanted to get the vaccine, or whether they have already had a possible reaction, I absolutely think that all of these people deserve a rating [a health care professional] so that we can hopefully continue with the vaccination, which I believe will be the case with the vast majority of patients, ”said Kelso.

Regarding revaccination, the current option for clinicians is to postpone the response based on the vaccine or adjuvant response, specify an additional waiting time to treat a response, use a graduated dosage, or administer and restrict the vaccine see what happens, Greenhawt said, noting that “Everyone has a different comfort [level] with this.”

“We are allergy sufferers … [and] We are trained to treat anaphylaxis. … The death toll from anaphylaxis is very small and I think people are very confused when they think that someone is going to have anaphylaxis and it is going to be fatal. It really isn’t. If you are responsible for taking precautions in your office and observing the patient, it is very unlikely, ”Greenhawt said.

For Greenhawt, “the greatest advice I can give here is … to talk to your patients about what they want. I cannot stress this enough. If you are really so afraid of the second dose and it does not suit your values ​​and your desires, this decision will be made for you. You don’t have to do anything other than ask them what they want. “

“In the end, I make suggestions [and] You make decisions. No decision is right for everyone. You have to weigh the risk here of either treating a response or treating COVID-19 and you have to weigh the cost to society for any person without immunity, “Greenhawt said.



Receive an email when new articles are published

Please enter your email address to receive an email when new articles are published . “data-action =” subscribe “> subscribe

We could not process your request. Please try again later. If you continue to have this problem, please contact [email protected].

Back to Healio

Annual meeting of the American Academy of Allergy, Asthma and Immunology

Annual meeting of the American Academy of Allergy, Asthma and Immunology

Related Articles