Moderna has become the second company to get emergency use authorisation for its anti-coronavirus vaccine from the US Food and Drug Administration (FDA), a week after the one developed by Pfizer received similar approval.

According to an official statement, the FDA has determined that the Moderna Covid-19 vaccine has met the statutory criteria for issuance of an emergency use authorisation (EUA).

"Congratulations, the Moderna vaccine is now available!" President Donald Trump tweeted soon after.

The FDA based its recommendation on the totality of scientific evidence shared by Moderna, including a data analysis from the pivotal phase three clinical study announced on November 30. The primary efficacy analysis conducted on 196 cases indicated a vaccine efficacy rate of 94.1 per cent.

This vaccine is for people aged 18 or older.

An immunisation drive using the vaccine developed by Pfizer has begun in the US earlier this week. Vice President Mike Pence took the shot publicly on Friday.

Health Secretary Alex Azar said, "To have two vaccines against a novel coronavirus authorized and distributed within a year is extraordinary, and to have one of these vaccines developed by scientists at the NIH (National Institutes of Health) should be a great source of pride for every member of the HHS family and every American."

National Institutes of Health was a partner in the development of Moderna's vaccine.

"Authorization of Moderna's vaccine means we can accelerate the vaccination of frontline healthcare workers and Americans in long-term-care facilities, and, ultimately, bring a faster end to this pandemic," Azar said.

Moderna said that its mRNA-1273 vaccine is now authorized for distribution and use under an emergency use authorization.

Delivery to the US government will begin immediately. Moderna will continue to gather additional data and plans to file a Biologics License Application (BLA) with the FDA requesting full licensure in 2021, it said.

"I am proud of what the Moderna team has achieved in collaboration with our partners. We were able to create and manufacture the Moderna COVID-19 Vaccine in 11 months from sequence to authorization while advancing clinical development with a phase one, phase two and pivotal phase three study of 30,000 participants," said Chief Executive Officer of Moderna St phane Bancel.

Allocation and distribution of the vaccine will be prioritised according to populations identified by the Centers for Disease Control and Prevention's (CDC) Advisory Committee on Immunization Practices (ACIP).

Approximately 20 million doses will be delivered to the US government by the end of December 2020. The company expects to have between 100 million and 125 million doses available globally in the first quarter of 2021, with 85-100 million of those available in the US, Moderna said.

Under Operation Warp Speed, the Department of Defense, in partnership with the Department of Health and Human Services and the CDC, will manage allocation and distribution of the vaccine in the United States.

"With the availability of two vaccines now for the prevention of COVID-19, the FDA has taken another crucial step in the fight against this global pandemic that is causing vast numbers of hospitalizations and deaths in the United States each day," said FDA Commissioner Stephen M Hahn.

He said through the FDA's open and transparent scientific review process, two COVID-19 vaccines have been authorized in an expedited timeframe while adhering to the rigorous standards for safety, effectiveness, and manufacturing quality needed to support emergency use authorization that the American people have come to expect from the FDA.

Congressman Michael Burgess, a member of the House Rules Committee and Republican Leader of the House Energy and Commerce Subcommittee on Health, said that having a second anti-coronavirus vaccine approved for emergency use in a span of one week is a shining example of American resourcefulness and the successful work done through Operation Warp Speed.

"I want to thank President Trump for putting American innovation first, our scientists and medical community, and the countless volunteers who have stepped up during this pandemic to serve on the front lines," she said.

"This second vaccine is a signal that we are nearing the end of this pandemic, but we cannot stop taking the proper precautions especially now that cold and flu season is in full swing.

"Please continue to wash your hands thoroughly, wear a mask if you are unable to properly social distance, and stay home if you are sick. At the start of this pandemic, America declared that we are in this together and together we will reach the end," Burgess said.