- Regulatory approval -The US became the sixth country to green-light the Pfizer vaccine on Friday night.It was a triumphant moment for the American giant and its German partner BioNTech, who started work on their product, based on experimental mRNA (messenger ribonucleic acid) technology, just 11 months ago.But the move, while expected, was not without controversy after it was widely reported that President Donald Trump had called the chief of the Food and Drug Administration (FDA) and threatened to fire him if he didn't issue emergency approval on Friday.On Saturday, FDA 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.