The head of the agency’s vaccine division, Vinay Prasad, has overruled pushback from career staffers.

The vaccine maker Moderna said on Tuesday that the Food and Drug Administration had notified the company that the agency would not review its mRNA flu vaccine, the latest sign of federal health policy...

The FDA sent Moderna a “refusal-to-file” letter earlier this month, saying the company’s study testing the vaccine wasn’t sufficient, and the agency wouldn’t take up the company’s request for approval...