Novavax applies to the F.D.A. for authorization of its Covid vaccine.

The pharmaceutical company Novavax said on Monday that it had submitted an application to the Food and Drug Administration seeking authorization for its long-delayed protein-based coronavirus vaccine.

It is not clear what, if any, role Novavax’s vaccine will play in the United States if it wins clearance. The federal government ordered 110 million doses of the shot in two deals reached with the company in 2020, but the United States is now flush with other vaccines and does not need more supplies.

Stan Erck, Novavax’s chief executive, said in a statement that the company was working closely with the United States government “to develop a plan which includes doses, manufacturing, timing, and ongoing clinical trial research for boosters and pediatrics to support their pandemic response.”

Novavax’s vaccine uses a more conventional approach than the vaccines that were more swiftly developed and authorized. That could make it appealing to people who are hesitant to be inoculated with vaccines like those from Pfizer-BioNTech and Moderna that use the newer messenger RNA technology. Novavax’s product uses tiny particles studded with viral proteins, mixed with an immune-boosting compound known as an adjuvant. The vaccine is given as two shots, spaced three weeks apart.

Novavax’s vaccine was found to be protective against illness caused by earlier versions of the virus. The company has said its vaccine can generate an immune response against the Omicron variant, though it remains to be seen how strong the protection will be.

In the early months of the pandemic, Novavax’s vaccine was one of six selected for financing under Operation Warp Speed, the Trump administration’s effort to accelerate vaccine development. But Novavax, a Maryland company that has that has never brought a product to market, lagged behind other vaccine developers. It struggled to build up its manufacturing capacity and to demonstrate the purity of its vaccines to regulators.

Novavax’s Operation Warp Speed contract originally promised the company $1.6 billion in support for research and manufacturing in exchange for 100 million doses for the United States. As of Novavax’s most recent regulatory filing in November, the contract ceiling had been revised up to $1.8 billion, and the company reported that it had already received about $900 million.

The Serum Institute of India, the world’s largest vaccine producer, has a license to make its own version of Novavax’s vaccine and recently began exporting doses to Indonesia and the Netherlands.