In the first day of vaccinating healthcare workers in the U.K. two severe adverse reactions occurred which have prompted the U.K. to not advise that anyone with a history of "serious allergic reactions" get the vaccine until it can be absolutely determined that the vaccine had nothing to do with these adverse reactions. The U.K. is also recommending that vaccines only be administered in facilities that have resuscitation equipment.
People with allergies were not permitted to participate in the drug trials which is why something like this would only come to light upon rolling it out to the public. I worry about all of those other people who were not permitted to be in the "safety" trials as well (pregnant women, anyone with a comorbidity, people over 65, etc.).
https://www.denverpost.com/2020/12/09/pfizer-covid-vaccine-allergic-reactions/