ABSTRACT
Severe allergic reactions to vaccines are rare and occur approximately once per million administrations. The most severe form of an immediate reaction is anaphylaxis, usually IgE-mediated, and may cause death. Immediate reactions with features of anaphylaxis have been reported after immunization with COVID-19 vaccines, mainly after the mRNA vaccines. The reported incidence of 2.5 to 4.7 events per million administrations of mRNA vaccines is higher than reported rates of anaphylaxis (1 per million) with other vaccines. Anaphylaxis after injection of other COVID-19 vaccines has also been reported, although to a lesser extent. Many individuals who experienced possible anaphylaxis to COVID-19 vaccines had a history of allergy to various other allergens. While a history of anaphylaxis to other substances (e.g., foods, drugs, insect stings) is not a contraindication to vaccination, it is recommended that such individuals remain for 30 minutes of observation after receiving the injection, rather than the 15 minutes recommended for all other vaccine recipients. History of anaphylaxis after receiving other vaccines or the first dose of COVID-19 vaccine is a contraindication of COVID-19 vaccine injection. As with any vaccine, all vaccination sites should be equipped with the medications (epinephrine) and staff required to treat possible anaphylactic reactions. Mast cell-mediated reactions may involve various combinations of up to 40 potential symptoms and signs, which typically begin within minutes to an hour of vaccination, but can rarely be delayed beyond this time frame. It is also essential to understand that some other reactions to vaccines can mimic anaphylaxis, including vasovagal reactions and anxiety-related symptoms.