https://www.cdc.gov/.../vac.../safety/allergic-reaction.html

If you have a severe allergic reaction to a COVID-19 vaccine

CDC  has learned of reports that some people have experienced severe  allergic reactions—also known as anaphylaxis—after getting a COVID-19  vaccine. As an example, an allergic reaction is considered severe when a  person needs to be treated with epinephrine or EpiPen© or if they must  go to the hospital.

If  you have had a severe allergic reaction to any ingredient in an mRNA  COVID-19 vaccine, you should not get either of the currently available  mRNA COVID-19 vaccines.  If you had a severe allergic reaction after  getting the first dose of an mRNA COVID-19 vaccine, CDC recommends that  you should not get the second dose.