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SYDNEY: Two people in the UK have experienced an allergic reaction to the Pfizer / BioNTech COVID-19 vaccine.
This prompted the UK drug regulator to issue cautionary advice earlier this week that “people with a significant history of allergic reactions” should not receive this vaccine for now.
This is an appropriate cautious move. Advice may change once we better understand the cause of these reactions.
Both people reportedly had known allergies and were on adrenaline auto-injectors, suggesting that they had a history of severe allergic reactions, such as anaphylaxis, a rapid and severe form of allergy.
READ: UK Issues Anaphylaxis Warning on Pfizer Vaccine Following Adverse Reactions
At this stage, we don’t have much more detail on reported allergic reactions to the vaccine.
An advisory panel from the US Food and Drug Administration (FDA) recommended authorization of the Pfizer / BioNTech vaccine for emergency use. If the FDA grants this approval, it would be the third country behind the UK and Canada to do so.
HOW COMMON ARE THESE TYPES OF REACTIONS?
Serious allergic reactions to vaccines are extremely rare, and anaphylaxis occurs after approximately one per million doses of vaccine.
Most of the reactions reported as possible allergic reactions to vaccines are probably not true allergies.
Regardless, each person is typically asked about their medical history by their immunization provider, including whether they have any known allergies, especially to a vaccine or its ingredients, prior to being vaccinated.
FILE PHOTO: A photo illustration showing a small bottle labeled “COVID-19 Coronavirus Vaccine” and a medical syringe in front of the Pfizer logo. (Photo: REUTERS / Dado Ruvic)
As almost all serious allergic reactions occur within 15 minutes of exposure to the trigger, it is common throughout the world to monitor patients for at least 15 minutes after vaccination.
READ: US FDA Advisory Panel Votes For Pfizer’s COVID-19 Vaccine
In Australia, it is recommended that any facility where vaccines are delivered be equipped with the equipment and personnel trained to recognize and treat allergic reactions. This applies to all vaccines, including COVID-19 vaccines.
WHAT TYPES OF ALLERGENS ARE WE TALKING ABOUT?
People can be allergic to a wide range of substances (called allergens), including foods and medicines. If someone has a known allergy to an ingredient in a vaccine, they may be advised not to get vaccinated.
The Pfizer / BioNTech COVID-19 vaccine does not contain any ingredients that commonly cause allergic reactions, and the UK drug regulator has published the full list of ingredients.
The two people who may have had an allergic reaction after the Pfizer vaccine are likely to be seen by an allergist / immunologist. If they are found to actually have anaphylaxis, it is unlikely that they will be given the second dose of the vaccine.
A file photo of a girl with eczema showing the condition of her skin on her arm (Photo: Ngau Kai Yan)
However, in some situations, people who have had allergic reactions after one dose may be given more doses of the same vaccine using a specialized approach, such as gradual dosing, which can avoid triggering a reaction.
This approach has yet to be reported for any COVID-19 vaccine.
ARE CLINICAL TRIALS NOT SUPPOSED TO SOLVE PROBLEMS LIKE THIS?
People with a history of severe allergic reactions to a vaccine or any ingredient in the Pfizer / BioNTech vaccine were not included in the late phase clinical trial of this vaccine.
This is a precaution designed to protect the safety of trial participants. Clinical trials generally focus on healthy people with no underlying medical conditions, although Pfizer’s phase 2/3 trial allowed enrollment of people with stable pre-existing chronic conditions.
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Once the safety and efficacy of a vaccine is well established in healthy people, it can be offered to other populations, such as people with serious underlying medical conditions.
This trial includes more than 40,000 participants and has shown that the vaccine is safe and well tolerated, without serious safety concerns. The incidence of allergic-type symptoms after vaccination was slightly higher in the vaccinated group with 0.63% compared to the placebo group with 0.51%; however, it is not clear whether this small difference is due to chance.
WHAT ARE THE IMPLICATIONS FOR PEOPLE WITH SIGNIFICANT ALLERGIES?
As for the implications of this latest news for people with major allergies, it’s too early to tell. We do not yet know if these reports were true allergic reactions.
There is also no theoretical reason to suspect that allergic reactions would be more common with COVID-19 vaccines than with other vaccines, even those using newer technologies.
As always, people should discuss their medical history with their vaccine provider, including any allergy history.
A needle is filled with a vial of Pfizer / BioNTech COVID-19 vaccine at the Royal Victoria Infirmary, on the first day of the largest immunization program in British history, in Newcastle, Britain, on December 8, 2020 (Photo: Owen Humphreys / Pool via REUTERS)
Since COVID-19 vaccines will be administered to millions of people around the world, it is inevitable that some adverse events will be reported. There is the possibility of an adverse reaction with any medication or vaccine, and that is why people are monitored after receiving a vaccine.
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It’s always important to consider the risks and benefits when considering getting vaccinated.
More than 1.5 million people have died from COVID-19 so far, and thousands more die every day. The benefits of vaccination will far outweigh the risks, particularly for priority population groups most vulnerable to COVID-19.
Continuous monitoring of the safety of the COVID-19 vaccine is also crucial and will allow us to detect side effects that may be very rare or that may be related to an underlying medical condition.
Hear from infectious disease experts discuss what a COVID-19 vaccine launch would look like on our Heart of the Matter podcast:
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Nicholas Wood is Associate Professor of Child and Adolescent Health Discipline at the University of Sydney and Ketaki Sharma is Clinical Professor of Child and Adolescent Health Discipline at the University of Sydney. This comment first appeared on The Conversation.
