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As the first Pfizer-BioNTech Covid-19 vaccine rolls out in the United States and Europe, the excitement has been somewhat dampened by a small number of responses among the first thousand beneficiaries: as of December 17, two people in the Kingdom United and one in the United States, had severe allergic reactions to shooting. They all recovered quickly.
This prompted British health officials to recommend that doctors monitor patients for 15 minutes after receiving the vaccine to watch for reactions, and that anyone with a history of anaphylaxis should not receive the vaccine. Although when the United States Food and Drug Administration first authorized the vaccine on December 11, it initially suggested that clinicians not administer this vaccine to patients with a history of anaphylaxis, it reversed its decision. two days later, before the first reports of anaphylaxis arrived on December 14.
Allergic reactions – and their most severe form, anaphylaxis – occur when a person is exposed to an allergen, a list of substances that can include everything from foods (nuts, shellfish, gluten) to other elements of the body. environment, such as animal dander, pollen, latex or bee stings. When an allergic person is exposed to this substance, their body perceives it as a threat, triggering an immune response that can range from mild inflammation to systemic shock, depending on the severity of the allergy.
Although it’s common to have an allergy – an estimated 50 million Americans have it – anaphylactic reactions, which affect more than one of the body’s systems, are relatively rare. These acute reactions can be life threatening if left untreated, which is why people with acute allergies often carry EpiPens (the active ingredient, epinephrine, works quickly in the body to prevent throat to shut down, which patients then follow with an antihistamine such as Benadryl more slowly calms the immune response).
Pfizer-BioNTech clinical trials excluded people with a history of anaphylaxis, so the rate of severe reactions seen in the trials – in 0.63% of vaccinees, versus 0.51% of placebo recipients – may be higher in the general population. But this is not the first vaccine to cause an allergic reaction.
The most common annual influenza vaccine is produced with eggs, so it contains a small amount of egg protein that can trigger allergic reactions in recipients who are allergic to eggs. It’s not much of a problem if you know you have an egg allergy – there are now versions of the flu shot that don’t contain an egg – but if you don’t know before you get the shot and you are not observed by a healthcare professional, it could be risky.
No one yet knows which ingredient in the Pfizer-BioNTech vaccine causes these rare but significant allergic reactions. Some healthcare professionals suspect that this is an ingredient called polyethylene glycol (PEG). PEG is common in all kinds of products, from skin care to laxatives. But in this vaccine, as well as in a few others, it is used in small amounts to stabilize the mixture. PEG has caused rare but serious allergic reactions in the past, which is why some experts suspect that it is the allergen of the new vaccine. But without further testing, it’s impossible to know for sure.
The good news is that if you get the vaccine and have an allergic reaction, your anaphylaxis is probably treatable. Allergic reactions usually occur within 30 minutes of exposure to an allergen, so make sure you can be watched after receiving the vaccine at an appropriate social distance from other patients.
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