UPDATE 5-FDA defends its decision to refuse Moderna's flu vaccine review

A U.S. ‌Food and ​Drug Administration official on Wednesday defended the agency's decision to not review Moderna's experimental flu ‌vaccine application, saying the company should have given a higher strength flu vaccine to older patients in the control arm of its trial.

The official ‌said at a press briefing that the trial - which included ‌patients 50 and older - should have ensured that patients over age 65 receive the stronger flu vaccine recommended for that age group. He said the agency was ⁠not ​making any determination ⁠on the vaccine itself and could consider the application for a younger age group ⁠were the company to resubmit.

On Tuesday evening, Moderna disclosed that the ​FDA had sent it a refusal-to-file letter in which it cited ⁠Moderna's choice to compare the vaccine to the standard dose flu vaccine in ⁠the trials ​as a reason for rejecting its application, driving shares down after hours. Shares were off about 4% in midafternoon after declining ⁠as much as 12% earlier in the day.