People line up to enter a mass COVID-19 vaccination site at the United Center in Chicago, the United States, on March 10, 2021.(Photo: Xinhua)

 
U.S. President Joe Biden announced on Wednesday that his administration will order another 100 million doses of the Johnson & Johnson COVID-19 vaccine.

The planned purchase would bring the country's total vaccine order to 800 million doses.

"On Saturday, we hit a record of 2.9 million vaccinations in one day in America," Biden said.

Biden said last week the United States would have enough COVID-19 vaccine doses for every adult American by the end of May, which would dramatically accelerate his timeline previously set for the end of July.

There are three COVID-19 vaccines currently authorized for emergency use in the United States.

The U.S. Food and Drug Administration authorized the one developed by American drugmaker Pfizer in partnership with German company BioNTech, and another by American drugmaker Moderna, in December last year.

Johnson & Johnson's COVID-19 vaccine was approved for emergency use on Feb. 27. It is the first single-dose vaccine authorized in the United States.

Over 127 million vaccine doses have been distributed across the United States as of Wednesday, and more than 95 million doses have been administered, according to the U.S. Centers for Disease Control and Prevention.