Trump vows Covid-19 vaccine will be ready in 2020
What is a vaccine and how is one made?
US President Donald Trump has vowed to deliver a coronavirus jab by year's end as he launched a White House vaccine initiative, dubbed "Operation Warp Speed".
The effort will begin with studies on 14 promising vaccine candidates for accelerated research and approval.
Progress is moving at "record speed", but the US must be prepared to reopen "vaccine or no vaccine," Mr Trump said.
Experts have cast doubt on the White House timelines for a jab.
What did Trump say?
Announcing 'Warp Speed' at a White House Rose Garden news conference on Friday, Mr Trump named an Army general and a former healthcare executive to lead the operation, a partnership between the government and private sector to find and distribute a vaccine.
Moncef Slaoui, who had previously headed the vaccines division at pharmaceutical giant GlaxoSmithKline, will lead the mission, while Gen Gustave Perna, who oversees distribution for the US Army, is to serve as chief operating officer.
Speaking after Mr Trump, Mr Slaoui said he was "confident" that a "few hundred million doses of vaccine" will be delivered by the end of 2020.
However, Mr Trump made clear that even without a vaccine, Americans must begin to return to their lives as normal.
"I don't want people to think this is all dependent on a vaccine," he said. Many experts say a vaccine is the only thing that will give Americans the confidence to fully reopen the economy in the absence of widespread testing.
"I think the schools should be back in the fall," Mr Trump added.
Elisa Granato was the first volunteer to be injected in a human trial
Earlier this week Dr Anthony Fauci, who serves on the coronavirus taskforce and appeared wearing a mask at the Rose Garden conference, testified to the Senate that it would be a "bridge too far" for schools to reopen in the autumn.
Dr Fauci and other experts have strongly suggested that a jab will take at least a year to develop.
As Mr Trump spoke, truck drivers who have parked around the White House for several weeks blared their horns in protest against low wages.
At one point, Mr Trump instructed a reporter to remove her mask so she could be better heard over the noise as she addressed him.
What other government coronavirus efforts are there?
'Warp Speed' is the latest of several Covid response projects Washington has undertaken.
In March, the White House launched a testing initiative, enlisting major pharmacy retailers like CVS, Walgreens and Rite Aid to set up drive-through testing sites throughout the country. Such partnerships have stalled, however, and the US has faced continued criticism for its lags in testing.
In recent weeks, the White House announced further efforts and has helped ramp up testing to nearly 10 million as of 15 May, according to the Our World in Data database.
Besides the new White House jab initiative, the Food and Drug Administration is also evaluating vaccine candidates for human trials.
On Friday, the US House of Representatives will vote on a coronavirus rescue package worth more than $3tn (£2.5) that allocates funds to local governments, expanded testing and another round of direct payments to Americans. The bill - which would be the largest aid package in US history - has already faced Republican opposition, with Mr Trump declaring the bill "dead on arrival".
Some health experts have remained sceptical about the rapid timeline for development and distribution proposed by the White House.
"I don't understand how that happens," said Dr Peter Hotez co-director of the Medicine Coronavirus Vaccine Team at Baylor College on CNN after Mr Trump's announcement.
While a vaccine could be manufactured in the coming months, "I just don't see" how there will be enough safety data for a general use vaccine, he said. "I don't see a path by which any vaccine is licensed for emergency use or otherwise till the third quarter of 2021."
Mr Slaoui acknowledged in an earlier interview with the New York Times that the timeline was ambitious, but said he "would not have committed unless I thought it was achievable".
