The company said on Thursday that is has received more than one billion US dollars (£820 million) from the US Biomedical Advanced Research and Development Authority (Barda) for the development, production and delivery of the vaccine, starting in autumn.
While not proven to be effective against the coronavirus, vaccines are seen by world leaders as the only real way to restart their stalled economies, and even to get an edge over global competitors.
The FTSE 100 pharmaceuticals giant said it had secured total manufacturing capacity for one billion doses so far, and would begin the first deliveries in September. Some officials are counting on a vaccine to allow America to return to normal life and the government isn't waiting for trial results to ramp up production.
Its development program will involve a Phase 3 clinical trial with 30,000 participants, as well as a pediatric trial.
"AstraZeneca is advancing its ongoing response to address the unprecedented challenges of COVID-19, collaborating with a number of countries and multilateral organisations to make the University of Oxford's vaccine widely accessible around the world in an equitable manner", a statement said.
"We are so proud to be collaborating with Oxford University to turn their ground-breaking work into a medicine that can be produced on a global scale", AstraZeneca CEO Pascal Soriot said in a statement Thursday.
But on Thursday, AstraZeneca said it was now engaging with worldwide organizations such as the World Health Organization "for the fair allocation and distribution of the vaccine around the world".
Some 300 million of the 400 million doses are set to go to the USA, where the Department of Health and Human Services announced it was collaborating with AstraZeneca to make the first ones available as early as October.
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The Oxford team is now testing the vaccine candidate in humans.
AstraZeneca office in South San Francisco, California, US.
There are now no approved treatments or vaccines for COVID-19 being tested by pharmaceutical giants across the world, with governments, drugmakers and researchers working on around 100 programs and experts predicting a safe and effective means of preventing the disease could take 12 to 18 months to develop.
Human trials of the vaccine developed by Oxford's Jenner Institute began last month, with hundreds of people in Britain volunteering to be part of the study. A Phase 1/Phase 2 clinical trial began in April with the data expected "shortly", according to the company.
Dr. Anthony Fauci, the country's leading infectious disease expert on the White House Coronavirus Task Force, said during a March 30 briefing that he thinks the vaccine will be ready for the public in 12 to 18 months.
Other drugmakers including Pfizer Inc, Johnson & Johnson and Sanofi are in various stages of vaccine development.
USA -based Inovio Pharmaceuticals said on Wednesday its experimental vaccine produced protective antibodies and immune system responses in mice and guinea pigs.