Feb 27 (Reuters) - Novavax's NVAX.O fourth-quarter loss narrowed on Thursday, helped by reduced selling and administrative expenses of COVID-19 vaccines, its only product on the market.

The company has struggled to keep up with the pace of its rivals Moderna MRNA.O and Pfizer PFE.N, which make messenger RNA-based vaccines compared to its protein-based shot.

Novavax reported quarterly sales of $49.8 million for COVID vaccines, down 80.2% from the year earlier.

The U.S. company signed a licensing deal worth at least $1.2 billion with French drugmaker Sanofi SASY.PA in May to hand over the rights to sell its vaccines in several markets, including the United States and Europe.

Maryland-based Novavax said it would continue to sell the shots in the U.S. during the first half of this year, as it transitions the market to Sanofi beginning with the 2025-2026 vaccination season.

It is banking on revenue from its Sanofi deal and vaccines in development, including an experimental COVID-flu combination shot and for bird flu, which is in pre-clinical stage.

Novavax said it was eligible to receive royalties in high teens to low twenties percent on Sanofi sales, along with $350 million in commercial launch payments associated with the COVID-flu combination products.

The vaccine maker did not provide total revenue forecast for 2025, as it is reliant on Sanofi's sales estimates for certain revenue components.

Shares of Novavax, along with other vaccine makers, took a hit this year after lawmakers advanced President Donald Trump's nomination of Robert F. Kennedy Jr. to head the Department of Health and Human Services towards confirmation.

An environmental lawyer and a vaccine critic, Kennedy was confirmed to the role on February 13.

Novavax's net loss was $81 million for the quarter ended December 31, compared with a net loss of $178.3 million a year ago.

It ended 2024 with $938 million in cash and receivables, compared to $584 million as of December 31, 2023.

(Reporting by Christy Santhosh in Bengaluru; Editing by Shilpi Majumdar)

((Christy.Santhosh@thomsonreuters.com))