![A nurse holds a vial of Pfizer's COVID-19 vaccine](https://www.gpb.org/sites/default/files/styles/flexheight/public/2020-12/pfizer-covid-19-vaccine-ap20344405054781.jpg?itok=MnUOpkE9)
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A nurse holds a phial of the Pfizer-BioNTech COVID-19 vaccine at Guy's Hospital in London, Tuesday, Dec. 8, 2020, as the U.K. health authorities rolled out a national mass vaccination program. U.K. regulators said Wednesday Dec. 9, 2020, that people who have a “significant history’’ of allergic reactions shouldn’t receive the new Pfizer/BioNTech vaccine while they investigate two adverse reactions that occurred on the first day of the country’s mass vaccination program.
Credit: Frank Augstein / AP