WASHINGTON - The US Food and Drug Administration (FDA) on Saturday authorized Johnson & Johnson's COVID-19 vaccine for emergency use in the United States.

It is the third COVID-19 vaccine that has received the FDA's emergency use authorization in the country, following the first one developed by American drugmaker Pfizer in partnership with German company BioNTech, and the second one developed by American drugmaker Moderna.

It is also the first single dose COVID-19 vaccine available in the United States.

The new federal authorization allows Johnson & Johnson's vaccine to be distributed in the United States for use in individuals 18 years of age and older, according to the FDA.

The totality of the available data provides clear evidence that the vaccine may be effective in preventing COVID-19, the FDA said in a statement.

The data also shows that the known and potential benefits of the vaccine outweigh its known and potential risks, which supports the company's request for the vaccine's use in people 18 years of age and older, said the FDA.

"The authorization of this vaccine expands the availability of vaccines, the best medical prevention method for COVID-19, to help us in the fight against this pandemic, which has claimed over half a million lives in the United States," said Acting FDA Commissioner Janet Woodcock.

The approval came a day after a key FDA advisory committee recommended authorizing the vaccine for emergency use.

Unlike the two-shot dosing for the vaccines from Pfizer-BioNTech and Moderna, the Johnson & Johnson vaccine only requires one shot. Meanwhile, it does not require ultra-cold storage.

The United States remains the nation worst hit by the pandemic, with more than 28 million cases and over half a million deaths, according to the Center for Systems Science and Engineering at Johns Hopkins University.

US President Joe Biden's national vaccination campaign aims to administer 100 million doses of two-stage coronavirus vaccines in his first 100 days in office.

Over 96 million vaccine doses have been distributed across the United States as of Saturday, and more than 72 million doses have been administered, the US Centers for Disease Control and Prevention's data shows.