Friday, the US Food and Drug Administration (FDA) opened an investigation as five people showed allergic reactions after they were administered Pfizer-BioNTech's COVID-19 vaccine this week.

The director of the FDA’s Center for Biologics Evaluation and Research, Peter Markssaid during a press conference that the allergic reactions had been reported in more than one state, including Alaska.

Additionally, he said that a chemical called polyethylene glycol (PEG) contained in the Pfizer vaccine, as well as the Moderna Inc vaccine which was authorized by the US Friday, "could be the culprit” causing the reactions.

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