The U.S. Food and Drug Administration granted on Saturday Johnson & Johnson's COVID-19 vaccine an emergency use approval, giving the country a third shot to contain the pandemic that has claimed the lives of more than 500,000 Americans, according to USA Today, Sunday.

Around 4 million doses of the new vaccine -- developed by Janssen Pharmaceuticals, a Johnson & Johnson company, should be made available next week.

Johnson & Johnson said it will have 20 million doses of the vaccine available in the U.S. by the end of March, and 100 million doses by the end of June.

Because the vaccine requires only one shot, it will help protect 100 million people and take effect faster compared to other pharmaceutical companies' two-dose treatment.

"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," NPR quoted acting FDA Commissioner Janet Woodcock as saying in a statement.

The FDA approval followed a positive recommendation from an expert panel that evaluated Johnson & Johnson's vaccine data from multiple clinical tests.

The study found Johnson & Johnson's vaccine to be 66% safe and effective in preventing mild to serious COVID-19 disease. For disease judged critical, the effectiveness was 85%. The study was conducted in the U.S., South Africa, and South America.

Its the first authorized treatment that uses a harmless virus to deliver DNA into cells, which then produce spike proteins that activate the immune system.

This is now the third COVID-19 vaccine that has been given Emergency Use Authorization, following the Pfizer/BioNTech and Moderna vaccines, which have been administered to almost 50 million Americans last year.

In a statement, U.S. President Joe Biden said Saturday's EUA means "there's a light at the end of the tunnel" but again emphasized the importance of reduction measures like social distancing and proper washing of hands.