By Sriparna Roy and Michael Erman

(Reuters) -The U.S. Food and Drug Administration said on Tuesday it authorized an updated version of Novavax's COVID-19 vaccine for emergency use in individuals aged 12 years and older, and the company's shares closed 8% higher.

The Maryland-based company, whose COVID vaccine is its lone marketed product, has adopted cost-cutting measures and is counting on commercial sales of its updated shot to help it stay afloat. The company has said it may not be able to remain solvent otherwise.

The U.S. Centers for Disease Control and Prevention (CDC) director last month signed off on broad use of rival updated COVID vaccines from Pfizer Inc with German partner BioNTech, and from Moderna. Those mRNA-based shots are recommended for use in people ages six months and up during the country's autumn vaccination campaign.

The CDC's Advisory Committee on Immunization Practices (ACIP) will not meet again to discuss the Novavax shot, a spokesperson said.

"ACIP's recommendation last month, which was then approved by the CDC director, was inclusive of all FDA-licensed or authorized updated COVID-19 vaccines including those expected to be licensed or authorized in the coming months," the spokesperson added.

Novavax, whose protein-based shot uses a technology employed for decades to combat diseases, missed out on the pandemic vaccine windfall enjoyed by mRNA rivals due to manufacturing issues that delayed filing for approval when COVID was raging.

Novavax's original COVID shot received U.S. authorization in July 2022, long after Pfizer and Moderna vaccines were in use.

Fewer than 90,000 Novavax shots had been administered as of early May, according to government data.

Novavax CEO John Jacobs said the company is waiting for the FDA to allow release of the first batch of the updated vaccine, which it expects to happen in the coming days.

"Potentially as early as this week, certainly we would expect by next week, shots in arms," Jacobs said in an interview.

He said the vaccine should be available in the "vast majority of retail establishments across the U.S." as well as healthcare providers and through government programs.

The U.S. government ended the COVID public health emergency declaration in May, handing over responsibility for vaccinations to the private sector.

With the government no longer footing the bill for millions of Americans, insurance coverage stumbles that have slowed uptake of rivals' new vaccines may allow Novavax to catch up, Jacobs said.

"There's a strong demand signal. This is just the very beginning of the season."

All three of the updated shots target the XBB.1.5 variant of the coronavirus. XBB.1.5. is an Omicron subvariant that was dominant in the U.S. for much of this year but has since been overtaken by other variants as the virus continues to mutate.

Novavax has set the list price of its shot at $130 per dose, about in line with the $120 list for the Pfizer/BioNTech vaccine and $129 for Moderna's.

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(Reporting by Sriparna Roy in Bengaluru; Editing by Bill Berkrot)