ANKARA The US drug regulator has declined to review Moderna’s application for an mRNA influenza vaccine, saying the company’s main late-stage study did not use the most appropriate comparison shot, the company said Tuesday. The Food and Drug Administration (FDA), the federal agency that evaluates the safety and effectiveness of medicines and vaccines before they can be sold in the US, issued a rare refusal-to-file letter for Moderna’s mRNA-1010 vaccine, saying the company’s late-stage study did