"We have never tried an mRNA vaccine in humans before."
False. This is the first mRNA vaccine that has been approved. They have been tried and tested in earlier trials.
https://investors.modernatx.com/news-releases/news-release-details/moderna-announces-positive-interim-phase-1-clinical-data
CAMBRIDGE, Mass., April 27, 2017 — Moderna Therapeutics, a clinical stage biotechnology company that is pioneering messenger RNA (mRNA) Therapeutics™ to create a new generation of transformative medicines for patients, today announcedpositive interim data from an ongoing Phase 1 study of mRNA-1440, an mRNA infectious disease vaccine against avian H10N8 influenza, demonstrating mRNA-1440 induced high levels of immunogenicity, and was safe and well tolerated. The findings were published online today in the journal Molecular Therapy.
Moderna is conducting a Phase 1 randomized, double-blind, placebo-controlled, dose-escalating study to evaluate the safety and immunogenicity of mRNA-1440 against H10N8 influenza in healthy adult subjects. H10N8 is a subtype of the influenza A virus, for which there are no approved vaccines.