Although its shares have nearly doubled this year, Moderna has struggled to convince investors that it is anything other than a pandemic-era success. Regulatory approval of its new flu vaccine points it in the right direction.

The Food and Drug Administration late Wednesday approved Moderna's mRNA-based flu vaccine, mFlusiva, for adults aged 50 and older. The decision came after months of back and forth sparked by the agency's refusal to review the vaccine in February.

Like Moderna's Covid-19 vaccines, mFlusiva harnesses the drugmaker's flagship messenger RNA platform, which provides the body's own cells with instructions on how to manufacture proteins in order to build an immune response against viruses.

Although Moderna expects to have the vaccine ready in time for the 2026-2027 flu season, analysts don't expect mFlusiva to generate meaningful revenue until the second half of 2027, seeing as Moderna missed the major pre-season contracting and purchasing cycles for the current year.

The approval marks the drugmaker's fifth approved product globally and fourth FDA-approved product. As earnings demonstrated last week, its bottom line continues to be dictated by its Covid-19 franchise, consisting of its Spikevax and mNEXSPIKE branded vaccines.

Crucially, the FDA clearance Wednesday is a step toward a combined Covid-flu shot, which Moderna pulled from review last year after regulators requested additional data. It's also a powerful validation of the company's mRNA technology, which has faced pushback from figures like Health and Human Services Secretary Robert F. Kennedy Jr.

Kennedy directed the cancellation of around $500 million worth of federal contracts for mRNA-based vaccines in late 2025, citing false claims that the vaccines led to "new mutations." He previously asserted that mRNA technology "poses more risks than benefits."

In February, the FDA declined to review Moderna's application for mFlusiva, issuing a controversial "refuse-to-file" letter. Then-head of FDA vaccine development Vinay Prasad, who has since left the agency, noted that Moderna tested its vaccine against a standard flu shot instead of Fluzone High-Dose, which the FDA recommends for older adults.

The agency reversed its decision just two days later. In June, an advisory committee voted unanimously to recommend mFlusiva for adults 50 and older.