Jan 31 (Reuters) - Novavax Inc said on Monday it has filed for emergency use authorization of its COVID-19 vaccine for U.S. adults, a long-awaited step for the company following months of struggles with development and manufacturing problems.

The filing is based on data provided to the U.S. Food and Drug Administration last month and results of two late-stage trials in the United States, Mexico and the UK that showed the protein-based vaccine had an overall efficacy of about 90%, the company said.

"We believe our vaccine offers a differentiated option... that can be an alternative to the portfolio of available vaccines to help fight the COVID-19 pandemic,” said Novavax Chief Executive Officer Stanley Erck in a statement.

Novavax's vaccine uses a different technology than the mRNA vaccines from Pfizer/BioNTech and Moderna or the Johnson and Johnson shot.

Novavax has had to delay its U.S. submission multiple times due to development and manufacturing setbacks. A report earlier this year said the methods Novavax used to test the efficacy of its vaccine had fallen short of regulators' standards.

Data released in June from a late-stage U.S. trial showed the vaccine was more than 90% effective against a variety of concerning coronavirus variants, including Delta.

Early data published in late December suggests the vaccine is also effective against the fast spreading Omicron variant, which is now the dominant version of the virus in the United States and most of the world.

The U.S. submission follows authorizations for the vaccine from the European Medicines Agency and the World Health Organization, clearing the way for its use in Europe as well as low- and middle-income countries.

Novavax and India's Serum Institute, the world's largest vaccine producer, had together committed to providing more than 1.1 billion doses to the COVAX international vaccine sharing program. (Reporting by Leroy Leo in Bangaluru and Carl O'Donnell in New York; Editing by Anil D'Silva and Bill Berkrot)