The U.S. Food and Drug Administration (FDA) has approved the world's first messenger RNA (mRNA)-based flu vaccine, developed by U.S. company Moderna.
The FDA said on the 6th (local time) that it approved Moderna's seasonal flu vaccine "mFLUSIVA" for adults ages 50 and older. Among them, it granted full approval for adults 50 to 64, and granted accelerated approval for those 65 and older on the condition that additional confirmatory clinical trials are completed.
Moderna plans to begin supplying mFLUSIVA in the United States within weeks and start vaccinations this fall.
mFLUSIVA delivers, in mRNA form, the blueprint for a flu virus surface protein into the body. When cells produce the antigen protein based on the mRNA, the immune system recognizes it and forms antibodies that respond to the flu virus. It works on the same principle as the COVID-19 mRNA Vaccine.
The approval was based on phase 3 clinical trial results involving 40,805 adults ages 50 and older in 11 countries.
In the trial, mFLUSIVA showed roughly 27% higher efficacy in preventing flu infection compared with standard-dose flu vaccines. Notably, in studies of those 65 and older, it induced antibody responses similar to or stronger than existing high-dose flu vaccines.
The mRNA approach has the advantage of responding more quickly to changes in circulating viruses than existing flu vaccines. Whereas existing flu vaccines produce antigens by cultivating viruses in fertilized eggs or cells, the mRNA Vaccine is designed based on viral genetic sequences. As a result, it can shorten vaccine design and production timelines, enabling the development of vaccines better matched to circulating strains.
The approval process for Moderna's mFLUSIVA was not smooth. Early this year, the FDA once refused to accept for review Moderna's application, citing reasons including that the comparator group for those 65 and older was a standard-dose vaccine rather than a high-dose-only vaccine.
Moderna subsequently revised and resubmitted its application to reflect a plan to conduct additional research in those 65 and older, and in June the FDA's independent advisory committee unanimously recommended approval.
Moderna plans to further confirm real-world preventive effectiveness in those 65 and older through postmarketing clinical trials.
A Moderna representative said, "Influenza remains a serious public health challenge, and mFLUSIVA will be an important new preventive option for middle-aged and older adults," adding, "This approval is a milestone showing that the mRNA platform can address public health problems through continued scientific innovation."