BOSTON (BLOOMBERG) - AstraZeneca Plc received more than US$1 billion (S$1.42 billion) in U.S. government funding for an experimental Covid-19 vaccine from the University of Oxford, a boost to one of the world's fastest-moving projects to develop a shot.

The investment accelerates a race to secure vaccine supplies, seen as a key step toward restarting global economies after a lockdown-induced slump.

Stock markets have been rising and falling on developments in research labs as investors weigh the prospects.

The British drugmaker received the money from the US Biomedical Advanced Research and Development Authority (Barda) and said it has secured capacity to make 1 billion doses.

Although AstraZeneca has said it expects to have shots ready as soon as September, the company's vaccine candidate is still in human trials, with no guarantee of success.

The funding for AstraZeneca is part of the Operation Warp Speed effort to secure vaccines for the US, according to a statement from the Health and Human Services Department.

Astra can receive up to US$1.2 billion under the agreement, and the US expects 300 million doses to be available as early as October.

The US "is making multiple major investments in developing and manufacturing promising vaccines long before they're approved so that a successful vaccine will reach the American people without a day wasted," HHS Secretary Alex Azar said.

Oxford's vaccine is the fourth to receive Barda support. The US agency has also provided funding for French pharmaceutical giant Sanofi, including US$30 million for its Covid vaccine and a U$226 million award in December to increase production capacity for its pandemic influenza vaccine.

A Covid vaccine developed by the company will probably go to Americans first if the company can successfully deliver one, Chief Executive Officer Paul Hudson said last week in an interview with Bloomberg News.

Sanofi said later that it would make the shot available everywhere. While the absence of a European counterpart to Barda has slowed efforts to secure supplies, Hudson said the French company is in talks with several governments on possible arrangements.

Supplying Britain with vaccine will be a priority for AstraZeneca, CEO Pascal Soriot has said. Astra plans to make as many as 30 million doses available in Britain by September and has committed to delivering 100 million this year.

Astra said it's working with groups including the World Health Organization, the Coalition for Epidemic Preparedness Innovations and Gavi, the Vaccine Alliance, on making sure the vaccine is allocated fairly.

The company said it has supply agreements for 400 million doses.

"Several more agreements are expected to deliver AstraZeneca's commitment to ensure global access," a spokesman said in an email. "These agreements are happening in parallel in order to ensure broad and equitable supply of the vaccine throughout the world at no profit during the pandemic."

The US funding will support a final-stage clinical trial with 30,000 participants, as well as tests in children, AstraZeneca said.

Some doubts have been raised about the potential effectiveness of the Oxford vaccine after early results in monkeys were released. While the shot may have protected animals against severe infections, the results were weak compared with those of a test of a vaccine under development by Sinovac Biotech in Beijing, said William Haseltine, a former Harvard University HIV researcher, in a blog post.

The comparison is inapt for studies carried out with different types of vaccines given in varying doses, in monkeys which were infected with different levels of virus, the Oxford researchers said in a statement.

"In the end it is the impact on clinical disease that matters," they said.

Dozens of other vaccine projects are under way around the world, from the US to China, drawing on major pharma giants, university labs and others.

Moderna Inc shares jumped earlier this week after the US biotech revealed positive early results from its experimental vaccine. President Xi Jinping of China has said any successful vaccine developed there will be made available as a global public good.