US health advisers are debating a new kind of flu vaccine Thursday, the first made with the same mRNA technology that was key to ending the Covid-19 pandemic.

Moderna is seeking Food and Drug Administration (FDA) approval of its new shot , dubbed mFlusiva, as an option for people 50 and older. The FDA advisory committee meeting is a step toward a final decision ahead of the winter flu season.

Tens of thousands of Americans die from influenza every year, and older adults are among the most vulnerable. There are various types of flu vaccines already available in the US, including three specifically recommended for people 65 and older. But vaccines made with the Nobel Prize-winning mRNA technology are faster to manufacture than other types – something experts say might help if the shape-shifting flu virus mutates in a way that requires suddenly brewing new doses to match.

In a study of 40,000 people age 50 and older, Moderna’s mRNA vaccine reduced flu cases by about 27% compared to those given another routinely used vaccine brand. Ahead of the meeting, FDA published a favorable review of that data and reported no safety concerns.

Moderna is seeking full approval for the vaccine’s use in the 50- to 64-year-old population – along with authorization for use in those 65 and older while it conducts additional testing.

Earlier this year, Moderna’s data was at the center of a highly unusual public dispute as a then-top FDA official blocked the company’s application for its first-of-its-kind shot.

The embattled vaccine chief at the time, Dr Vinay Prasad, said the company should have compared its shot to a high-dose flu vaccine recommended for seniors rather than a standard-dose brand. It was a sign of FDA’s heightened vaccine scrutiny under the health secretary, Robert F Kennedy Jr.

Moderna challenged that decision, noting that FDA staff had approved that main study’s design and citing a separate, smaller study comparing the mRNA shot with a high-dose vaccine for seniors. Days after the spat, the FDA accepted Moderna’s application.

The expert panel also will assess that smaller study, which found Moderna’s shot generated flu-fighting antibodies similarly to a high-dose senior shot. The FDA’s initial review noted the new vaccine lacks data on very frail older adults and those with weak immune systems.