President Donald Trump celebrated the expected approval of the first U.S. vaccine for the coronavirus as the White House worked on Tuesday to instill confidence in the massive distribution effort that will largely be executed by President-elect Joe Biden Trump declared that the expected approvals are coming before most people thought possible. “They say it’s somewhat of a miracle and I think that’s true," Trump said. He led the event celebrating “Operation Warp Speed,” his administration's effort to produce and distribute safe and effective vaccines for COVID-19. The first vaccine, from drugmaker Pfizer, is expected to receive endorsement by a panel of Food and Drug Administration advisers as soon as this week, with delivery of 100 million doses - enough for 50 million Americans - expected in coming months. “Every American who wants the vaccine will be able to get the vaccine and we think by spring we’re going to be in a position nobody would have believed possible just a few months ago,” Trump said. Trump and his aides hope the event will tamp down skepticism among some Americans about the vaccine and help build the outgoing Republican president’s legacy. The “Operation Warp Speed” summit featured Trump, Vice President Mike Pence and a host of government experts, state leaders and business executives, as the White House looks to explain that the vaccine is safe and lay out the administration’s plans to bring it to the American people. But officials from Biden’s transition team, which will oversee the bulk of the largest vaccination program in the nation’s history once he takes office Jan. 20, were not invited. Trump's administration was facing new scrutiny Tuesday after failing to lock in a chance to buy millions of additional doses of Pfizer's vaccine, which has shown to be highly effective against COVID-19. That decision could delay the delivery of a second batch of doses until Pfizer fulfills other international contracts. Under its contract with Pfizer, the Trump administration committed to buy an initial 100 million doses, with an option to purchase as much as five times more. But this summer, the White House opted not to lock in an additional 100 million doses for delivery in the second quarter of 2021, according to people who spoke on condition of anonymity because they were not authorized to discuss it publicly. Trump used the event to sign an executive order in which the secretary of Health and Human Services is directed to ensure that Americans have priority access to the vaccine. Concerns about the availability of the vaccines come as Trump signed an executive order to prioritize Americans for coronavirus vaccines procured by the federal government. A senior administration official said the order would restrict the government from delivering doses to other nations until there is excess supply to meet domestic demand, but it was not immediately clear what the practical impact would be. The Food and Drug Administration's panel of outside vaccine experts is to meet Thursday to conduct a final review of the Pfizer drug, and it will meet later this month on the Moderna vaccine. The FDA is not required to follow the panel's advice, though it usually does. Subscribe to our YouTube channel: https://bit.ly/2TwO8Gm Bloomberg Quicktake brings you live global news and original shows spanning business, technology, politics and culture. Make sense of the stories changing your business and your world. To watch complete coverage on Bloomberg Quicktake 24/7, visit http://www.bloomberg.com/qt/live, or watch on Apple TV, Roku, Samsung Smart TV, Fire TV and Android TV on the Bloomberg app. Have a story to tell? Fill out this survey for a chance to have it featured on Bloomberg Quicktake: https://cor.us/surveys/27AF30 Connect with us on… YouTube: https://www.youtube.com/user/Bloomberg Breaking News on YouTube: https://www.youtube.com/c/BloombergQuickTakeNews Twitter: https://twitter.com/quicktake Facebook: https://www.facebook.com/quicktake Instagram: https://www.instagram.com/quicktake