Moderna has been approved by the US government as the country's second Covid-19 vaccine, clearing the way for millions of doses to be released.
The Moderna Covid-19 vaccine has been approved by the FDA. Photo: David Himbert / Hans Lucas/ AFP
The Food and Drug Administration (FDA) authorised the US-made vaccine about a week after approving a Pfizer/BioNTech vaccine, which is now being distributed.
The US has agreed to purchase 200 million doses of Moderna, and six million may be ready to ship now.
The country has the world's highest numbers of Covid-19 deaths and cases.
It has recorded at least 311,529 deaths and 17,269,542 infections, according to Johns Hopkins University.
"To go from having a sequence of a virus in January to having two vaccines available in December is a remarkable achievement," said Dr James Hildreth, CEO of Meharry Medical College in Tennessee.
An FDA advisory panel on Thursday voted 20-0 with one abstention that the benefits of the Moderna vaccine outweighed the risks for those aged 18 and over, and authorisation followed on Friday.
Regulators reported earlier this week that the Moderna vaccine was safe and 94 percent effective.
US President Donald Trump, who hours before the official announcement tweeted that the vaccine had been "overwhelmingly approved" and distribution would "start immediately", celebrated the news.
How does Moderna differ from the Pfizer jab?
It requires temperatures of around -20C for shipping - similar to a normal freezer.
The vaccine manufactured by US corporation Pfizer and Germany's BioNTech SE requires temperatures closer to -75C, making transport logistics much more difficult.
Like the Pfizer jab, the Moderna vaccine also requires a second booster shot. Moderna's second injection comes 28 days after the first, compared with 21 for Pfizer.
Moderna is based in Cambridge, Massachusetts, and had previously said that the "vast majority" of its doses would be manufactured there.
Pfizer/BioNTech is being manufactured in several countries, including Germany and Belgium.
Other countries have also ordered the Moderna vaccine:
* Canada plans to get two million doses by March - part of a total 56m doses.
* The UK has already pre-ordered seven million doses.
* The European Union last month announced a contract to purchase 80m doses - with an option to purchase up to 80m more - once the vaccine is deemed safe and effective.
* Japan has signed up for 50m doses, South Korea for 20m, and Switzerland has ordered 7.5m, according to data compiled by the Duke University Global Health Innovation Center
Who is first in line in the US?
The US vaccination programme aims to reach 50m people by April.
New York nurse Sandra Lindsay was among the first people in the country to receive a coronavirus vaccine when the Pfizer/BioNTech rollout began on Monday.
Footage of her being vaccinated was streamed on the Twitter feed of New York Governor Andrew Cuomo, whose state was the epicentre of the US epidemic in the first wave earlier this year.
"I hope this marks the beginning of the end of a very painful time in our history. I want to instil public confidence that the vaccine is safe. We're in a pandemic and so we all need to do our part," Lindsay said.
Centers for Disease Control and Prevention guidelines submitted to US states say healthcare workers should be prioritised first, as well Americans living in long-term care homes.
Essential workers are expected to be next in line, but it will be up to states to decide which industries to prioritise.
Moncef Slaoui, the chief scientist of federal vaccine distribution programme Operation Warp Speed, said the young and healthy should be at the back of the queue.
At least 70 percent or 80 percent of the US population need to be vaccinated to achieve herd immunity, he said.
- BBC