Vaccine allergy? Experts say most past reactions don’t justify exemptions
Dr Mariam Hanna has noticed an increase in requests for allergy assessments at her clinic in Burlington, Ont., After the province began implementing COVID-19 vaccine certificates last month.
Whether people have delayed their vaccinations due to a past reaction or are asking for an exemption from inoculation warrants, Hanna said a past allergic response doesn’t mean you can’t get the shot.
Allergists across the country have safely vaccinated most patients who come to their clinics, regardless of their allergic history, she said.
“Whether it’s as an excuse, a misunderstanding or miscommunication, we definitely get a lot of referrals because of (vaccine rules),” said Hanna, assistant clinical professor at McMaster University.
“Most of the time, that’s not a ground for exemption.”
Hanna said many patients she assesses are concerned about past reactions to non-COVID-19 vaccines. But because Pfizer-BioNTech and Moderna mRNA injections are different from typical inoculations, these past reactions usually do not recur.
Other patients worry about receiving a second dose of mRNA if they have had an adverse reaction to the first. But she said many patients mistake common non-life-threatening reactions – including rashes or swelling at the injection site – for an allergy.
“It’s only the very, very rare patients who have had a systemic reaction, usually within 15 to 20 minutes of receiving the first dose, that we want to watch out for,” Hanna said. “Most of the side effects you would expect from a vaccine are not contraindications to the exemption.
“And sometimes you need an allergist to help you clear it up.”
Allergists assess patients at their specialty clinics, taking a full history to determine the severity of the previous allergic experience – and if it was an allergic reaction at all.
The evaluation can sometimes include skin testing, where an ingredient in the vaccine is spread over a small patch of skin, but Hanna said each patient’s appointment will be different.
Dr Samira Jeimy, an expert in clinical immunology and allergology at Western University, said even those who experienced what they perceived to be strong allergic reactions could be wrong.
Some non-allergic reactions can include anxiety-related events that mimic allergic reactions, she said, including hyperventilation, fainting, and even symptoms that resemble anaphylaxis – a serious and life-threatening reaction where the blood pressure drops and the airways narrow, making it difficult to breathe.
“Things that mimic anaphylaxis are much more common than actual anaphylaxis,” Jeimy said. “One example is vocal cord dysfunction, where someone might actually get their vocal cords snapped (when) nervous.”
The Canadian Society of Allergy and Clinical Immunology says the risk of systemic allergic reactions, including anaphylaxis, is extremely rare. Studies suggest that the estimated annual rate of anaphylaxis in Canada is approximately 0.4 to 1.8 cases per million doses of vaccine administered.
According to Health Canada’s review of vaccine adverse reactions, 307 cases of anaphylaxis have been reported nationwide, out of more than 56 million doses of COVID-19 administered.
Jeimy said his clinic in London, Ont., Had been able to immunize “about 99%” of people with allergies.
This includes those who have had real and serious reactions to a first dose of the COVID-19 vaccine.
Allergists work around this problem by giving a person with a confirmed allergy small amounts of the dose, separated by observation periods of 15 to 30 minutes, until the dosage is complete.
Jeimy said it can take hours to complete a graduated administration for extreme cases.
“If I think the patient is at moderate risk for a reaction, I will divide the vaccine into three or four doses,” she said. “If the patient is at higher risk, I will extend the dosage further.”
Canada’s National Advisory Committee on Immunization says COVID-19 vaccines should not be offered “routinely” to those who have had a severe allergic reaction after the first dose. If a risk assessment finds that the benefits of vaccination outweigh the risks of allergy, NACI indicates that a different vaccine than the one that caused the initial reaction – either the AstraZeneca viral vector or the products mRNA – can be used to complete the two-dose series.
Jeimy said her clinic carries doses of AstraZeneca for emergency situations, but she hasn’t had to use them. Instead, most people can safely complete a two-dose series of mRNA.
Jeimy said allergists are not sure which component of mRNA vaccines causes severe allergic reactions in a small number of people. But PEG, or polyethylene glycol, is “currently considered the culprit.” She added that allergies to PEG on skin tests do not necessarily “correlate with tolerance to the vaccine,” however.
PEG is a common ingredient in cosmetics, skin care products, and some medications, including Tylenol and cough syrup, Jeimy said. So people who are allergic to PEG probably know they have it long before they get an mRNA vaccine.
The NACI says a COVID-19 vaccine “should not be routinely offered to people who are allergic to any component” of the vaccine.
Jeimy urges people to seek clarification from a doctor before swearing not to receive COVID-19 vaccines.
“I don’t think there is any point in avoiding things preemptively for fear of a reaction,” she said. “You have a much higher risk of infection with COVID-19. “