WASHINGTON (AP) - Pfizer and BioNTech will supply the U.S. with an additional 100 million doses of the COVID-19 vaccine under a new agreement.The drugmakers said Wednesday that they expect to deliver all the doses by July 31.Pfizer already has a contract to supply the government with 100 million doses of its vaccine, which requires two doses per patient.RELATED: US negotiating with Pfizer for millions more doses of COVID-19 vaccine Under the $2 billion deal announced Wednesday, the companies will deliver at least 70 million of the additional doses by June 30, with the remaining 30 million doses to be delivered no later than July 31.