With the latest deal, the companies now will deliver up to 200 million doses to the US.
Both firms plan to supply the full 200 million doses to Operation Warp Speed (OWS) by 31 July 2021.
In July this year, the US government first placed an order worth $1.95bn with Pfizer and BioNTech to procure 100 million doses of their BNT162 vaccine candidate for Covid-19.
BNT162, which is being developed for giving protection against SARS-CoV-2, was secured fast track designation from the US Food and Drug Administration (FDA) in July.
Recently, the companies have secured emergency use authorisation (EUA) from the FDA for their vaccine to prevent Covid-19 in individuals 16 years of age and older.
BioNTech CEO and co-founder Dr Ugur Sahin said: “We regard the US government’s order of additional doses from their vaccine contingent as a clear sign of confidence and trust in our vaccine and our ability to deliver. Our goal remains to bring a safe and effective Covid-19 vaccine to as many people as we can all around the world.”
As per terms of the second deal, Pfizer and BioNTech will supply up to 70 million of the additional doses by 30 June 2021. The companies intend to deliver the remaining 30 million doses by 31 July 2021.
The government is also having an option to order for up to an additional 400 million doses of the Pfizer-BioNTech vaccine.
Pfizer chairman and CEO Albert Bourla said: “With these 100 million additional doses, the United States will be able to protect more individuals and hopefully end this devastating pandemic more quickly.
“We look forward to continuing our work with the U.S. government and healthcare providers around the country.”