Serious allergic reactions, such as anaphylaxis, in the minutes following vaccination are rare but are possible with any vaccine. Every vaccination site should have staff available who are trained and equipped to recognize and respond to signs of anaphylaxis in a vaccine recipient. See this CDC website for additional information about preparing for the management of anaphylaxis following COVID-19 vaccination: www.cdc.gov/vaccines/covid-19/clinical-considerations/managing-anaphylaxis.html?anaphylaxis-management.html.
Anaphylaxis following vaccination with mRNA COVID-19 vaccines is reported at a rate of approximately 2 to 5 cases per million doses administered.
An immediate severe allergic reaction to any component or previous dose of any mRNA COVID-19 vaccine is a contraindication to vaccination with both the Pfizer-BioNTech and Moderna vaccines (all formulations); however, such a reaction is generally a precaution to the use of the Novavax vaccine; see the CDC’s COVID-19 interim clinical considerations section on contraindications and precautions for details: www.cdc.gov/vaccines/covid-19/clinical-considerations/interim-considerations-us.html#contraindications.
CDC also provides specific COVID-19 vaccination guidance for people with a history of allergies or allergic reactions: www.cdc.gov/vaccines/covid-19/clinical-considerations/interim-considerations-us.html#history-allergies-reactions.