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America finally has an mRNA flu shot. Now comes the fight to actually use it.

A weekly dose of stories chronicling progress around the world.

On August 5, 2026 — one year to the day later — the Food and Drug Administration (FDA) approved mFLUSIVA, the first mRNA influenza vaccine ever licensed in the United States.

That symmetry, while highly useful to writers like myself who are always looking to identify the rhymes of history, wasn’t planned. The approval landed on the one-year anniversary simply because of the deadline the agency had set for itself in February of this year, after it refused to review Moderna’s application and then, 15 days later, reversed itself.

So a better flu vaccine matters. But the more interesting thing is what the approval says about the year that produced it. The nine experts who voted unanimously that this vaccine’s benefits outweigh its risks were appointed under the very same secretary who was against mRNA technology. Asked to look at the evidence, those experts couldn’t produce a single vote against it.

That’s not quite a change of heart, but at a dark time for public health, it’s something to hang our hopes on — because flu could just be the start for this technology.

Every flu vaccine Americans have received since the 1940s has been grown inside fertilized chicken eggs. It’s a laborious process, closer to agriculture than it is high technology. Each batch incubates for nine to 12 days; the World Health Organization then spends months making the reagents manufacturers need to calibrate doses. The whole sequence runs about six months.

That means that the flu strains in your vaccine in November were selected back in February. Which is a problem, because flu viruses don’t like to stand still. Between February and November, the virus drifts, and the current dominant H3N2 flu drifts especially fast.

The eggs are a problem, too. Growing flu virus in a chicken egg forces it to adapt to egg cells, and those adaptations alter the very surface protein the vaccine is meant to teach your immune system to recognize. Between the 2011 and 2020 flu seasons, egg-adaptive mutations caused more mismatches than the virus’s own drift did. And more mismatches mean a less effective vaccine — while the flu shot prevented an estimated 12,000 deaths in the 2024–25 flu season, it is the weakest vaccine in routine American use, landing anywhere between 20 and 60 percent effective depending on how well February’s guess matched November’s virus.

mRNA skips the egg. The shot carries instructions, a strip of genetic code that tells your own cells to build the flu’s surface protein, which your immune system then learns to attack. And swapping in a new strain means retyping that code, not growing a new virus.

As a result, Moderna told the FDA’s advisory panel it can go from strain selection to finished vaccine in two to three months instead of six. That means strain picks could move later, closer to the season they cover, and a novel flu virus surfacing in September could still be blocked by a reformulated vaccine in the same season. Eggs are great, but they can’t do that.

Back in January I wrote here about the universal flu vaccine — one shot covering every strain for years. It’s a public health dream. mFLUSIVA isn’t that, but some of the best hopes for a universal flu vaccine run through the mRNA platform, and platforms only improve when somebody uses them.

That word — platform — is where last August’s decision went wrong. Kennedy made a claim about one application, mRNA respiratory vaccines, and cut funding for the technology underneath all of them. But over the 12 months that followed, the science on mRNA kept flowing.

In June, five-year melanoma results showed an individualized mRNA therapy given after surgery alongside pembrolizumab cut the risk of recurrence or death by 49 percent. In April, a Memorial Sloan Kettering team reported that among pancreatic cancer patients whose immune systems responded to a personalized mRNA vaccine, nearly 90 percent were alive six years later; the five-year survival rate in that disease sits near 13 percent. And KJ Muldoon, the first person treated with a gene-editing therapy built for his mutation alone, is walking and talking, though half the infants born with his disorder never see a first birthday. The editor that rewrote his DNA was delivered to his liver as messenger RNA — mRNA as the delivery truck rather than the vaccine.

None of those is a flu shot. All of them are the same chemistry — a strip of genetic code wrapped in a lipid nanoparticle — and none of them were what Kennedy was talking about when he defunded it.

Partially as a result, Americans are falling behind. Moderna’s combined Covid-and-flu shot is already licensed in Europe while patients here wait for a resubmission. The Phase 3 trial of its H5 bird flu vaccine — the one meant to be ready if bird flu ever learns to spread between people — runs on money from CEPI, the Coalition for Epidemic Preparedness Innovations, and the British government, after the administration killed a $760 million BARDA contract. “The United States invented this platform,” Johns Hopkins RNA biologist Jeff Coller wrote on Thursday, “and is the only country walking away from it.”

mFLUSIVA beat a standard-dose flu shot by 26.6 percent in a 40,700-person trial. (Against flu bad enough to send someone to a doctor, the figure was 33.7 percent — an exploratory finding the trial wasn’t built to prove, but that points in the same direction.) This is a better flu shot, but it hasn’t solved flu.

There are issues with side effects: two-thirds of recipients reported injection-site pain, against 30 percent for the comparison. Most cleared in a day or two, but in a country where a quarter of the people who skip the flu shot cite side effects, that’s not a minor problem.

And approval, unfortunately, isn’t access. The CDC’s vaccine advisory committee has been frozen by a federal court since March, so there is no clinical recommendation, which means insurers aren’t required to cover mFLUSIVA at no cost. The $500 million in canceled contracts hasn’t been restored. As Michael Osterholm, who runs the University of Minnesota’s infectious disease center, put it after the government reversed its mRNA decision in February: “We don’t have any idea why they reversed course. That’s part of the problem.”

The most optimistic reading is that nine independent experts appointed by this government looked at the evidence on mRNA and could not produce a single vote against it. The more pessimistic one is that it took a refusal-to-file letter, a public outcry and two senior departures to get there.

But here’s what we do know: Some morning this fall a 58-year-old will roll up a sleeve at a CVS for a vaccine designed off a sequence rather than grown in an egg, and will think about none of this. That’s more progress than I would have expected a year ago.

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