Moderna is seeking approval for a fourth COVID-19 vaccination shot, pending a grant for emergency authorization use from the Food and Drug Administration, the company announced Thursday.

If approved, this would be the second booster shot Moderna has issued for people ages 18 and up.

"The request to include adults over 18 years of age was made to provide flexibility for the U.S. Centers for Disease Control and Prevention (CDC) and healthcare providers to determine the appropriate use of an additional booster dose of mRNA-1273, including for those at higher risk of COVID-19," the company said in a statement.

The decision to request an additional dose stemmed from data in the U.S. and Israel on the impacts of the omicron variant, the statement said.

The first dose, which was administered as a pair, was approved by the FDA under emergency use in December 2020, while Moderna's first booster shot was authorized for emergency use in November 2021.

The FDA fully authorized Moderna's existing COVID-19 vaccine doses in January.

Dr. Eric Topol, founder and director of the Scripps Research Translational Institute, told NPR's Rob Stein that there is enough evidence to move forward with another booster dose.

"We need to move on this because [there] are a large group of people who have lost their protection against severe illness from Omicron and future variants," he said.

Some experts are not sold on the need for another dose right now.

"I think you'd want to have really convincing evidence that a second booster was needed and beneficial and we just don't have that," said Dr. Jesse Goodman, a former chief FDA scientist. "I don't think we know that a booster will not ultimately be required, but we're just not there yet."

Drugmakers Moderna and Pfizer-BioNTech require two initial doses and then a third shot to protect against COVID-19. Earlier this week, Pfizer and BioNTech sought FDA approval for a second booster shot for people 65 and older.

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