The US Food and Drug Administration defended itself from allegations of political pressure over the timing of its Pfizer-BioNTech Covid vaccine approval and provided new information on the risks to people with allergies.

The FDA issued an emergency use authorisation for the two-dose regimen late on Friday night following reports US President Donald Trump had threatened to fire the head of the agency if he didn't act that day, according to AFP.

Commissioner Stephen Hahn denied this had occurred, telling reporters: “The representations in the press that I was threatened to be fired if we didn't get it done by a certain date is inaccurate.”

He added that the decision, which had been expected a few days later, was “based on the strongest scientific integrity”.