New Delhi, Feb. 11 -- The US Food and Drug Administration has declined to review Moderna's approval application for its novel mRNA flu vaccine, causing a fall in the company's shares on late Tuesday.

Moderna on Tuesday said in a statement that the FDA had declined the application saying that its studies didn't compare the experimental shot to the "best-available standard of care."

The shares of Moderna fell around 11% during extended trading on Tuesday. So far this

The FDA said in its refusal letter that the company's approach to compare mRNA-1010 to an already licensed standard-dose seasonal influenza was the only reason why it declined to initiate a review of the application.

The letter in particular cited the lack of an "adequate a...