Novavax has formally asked the Food and Drug Administration to authorize its COVID-19 vaccine for emergency use, potentially bringing a fourth inoculation to the United States.

The Maryland-based drugmaker submitted its request along with data from two late-stage trials – one in the U.S. and Mexico, and one in the United Kingdom – which showed that the protein-based vaccine was 90% effective and had a "reassuring safety profile," though the trials took place before the omicron variant was dominant.

"We're extremely proud of the work of our teams and we look forward to FDA's review of our EUA request," Stanley Erck, the country's president and CEO, said in a statement. "We believe our vaccine offers a differentiated option built on a well-understood protein-based vaccine platform that can be an alternative to the portfolio of available vaccines to help fight the COVID-19 pandemic."

The European Union and the World Health Organization cleared the Novavax vaccine for emergency use in December. Australia authorized the vaccine earlier this month.

The vaccine is given in a two dose course, 21 days apart. The vaccine can be stored at normal refrigeration temperatures, 35°F to 46°F.

Erck told CNN in November of 2021 that once authorized, the first 100 million doses of its vaccine will be ready to ship.

The Novavax vaccine is produced more differently than other widely used COVID-19 shots: It's a protein vaccine, made with an older technology that’s been used for years to produce other kinds of vaccines. Novavax uses genetic engineering to grow harmless copies of the coronavirus spike protein in insect cells. Scientists extract and purify the protein and then mix in an immune-boosting chemical.