Cambridge, Massachusetts - Moderna said Wednesday the US Food and Drug Administration (FDA) had approved its new influenza vaccine, nearly six months after the regulator briefly rejected an application for review.

The company's first mRNA-based flu vaccine, mFLUSIVA, has been approved for use in all adults age 50 and older, the pharmaceutical firm said in a release.

"Moderna expects to have mFLUVISA available for eligible populations in the US for the 2026-2027 respiratory virus season," the release said.

Moderna went public with news in February that federal vaccine regulators had called its clinical trials inadequate and rejected their application for review of the new shot.

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But the FDA walked back its previous position a week later, after what Moderna called a "constructive" meeting.

The new shot uses mRNA technology, which health chief Robert F. Kennedy Jr., a vocal vaccine skeptic, has criticized. He notably cut off federal research grants that funded mRNA development.

Under Kennedy, and President Donald Trump, the FDA has called for a reconsideration of approval procedures for certain vaccines, including for influenza, along with proposed federal policy changes that have triggered widespread alarm among public health and medical professionals.

During his first term, Trump called mRNA technology a "modern-day miracle." It was used during the Covid-19 pandemic to swiftly develop an immunization against the fast-spreading illness, and was credited with saving millions of lives.

Vaccines against Covid-19 are considered safe and effective by global health authorities, and protect against the most severe forms of the infection.