Moderna’s mRNA-1010, an influenza vaccine made with messenger RNA, was tested against a licensed standard-dose flu shot in a phase 3 trial of adults 50 years and older. It prevented more laboratory-confirmed flu than the standard shot. That result covers everyone 50 and older as a single group, measured against a standard-dose comparator.
Key takeaways
- In the phase 3 trial published in the New England Journal of Medicine, confirmed flu illness occurred in 2.0% of mRNA-1010 recipients versus 2.8% of those given a standard-dose shot, about 27% fewer cases.
- The comparison shot was a standard-dose vaccine, not the high-dose or adjuvanted vaccines already recommended for people over 65.
- The mRNA shot caused more short-term reactions: injection-site pain in 65.8% of recipients versus 29.8%, and fatigue in 45.1% versus 20.3%.
What the study found
The pivotal Fluent trial (NCT06602024) was reported in the New England Journal of Medicine on May 7, 2026. It enrolled adults aged 50 and older, and 40,703 of them received a shot: 20,350 got trivalent mRNA-1010 and 20,353 got a licensed standard-dose comparator. Median follow-up was 181 days.
Confirmed influenza-like illness, verified by PCR testing, occurred in 411 of 20,179 mRNA-1010 recipients (2.0%) and 557 of 20,124 comparator recipients (2.8%). That works out to about 27% fewer cases (relative vaccine efficacy 26.6%), and the true benefit is very likely somewhere between 17% and 35% fewer (95% CI, 16.7 to 35.4).
In absolute terms, that gap of about 0.7 percentage points comes to roughly 7 fewer confirmed flu illnesses per 1,000 people vaccinated, or about one illness prevented for every 137 people who got the mRNA shot instead of the standard one.
The new shot was harder on people. Injection-site pain was reported by 65.8% versus 29.8%, fatigue by 45.1% versus 20.3%, headache by 37.8% versus 18.0%, and muscle pain by 35.4% versus 11.6%. Most reactions were mild to moderate and transient. Serious adverse events were similar, 2.2% versus 1.9%.
Dr. Kumar’s take
The headline number was earned against the wrong opponent for the people who need this vaccine most. The only vaccine mRNA-1010 was measured against here was a licensed standard-dose shot. Beating the standard dose says nothing about beating any other flu vaccine.
That is exactly the objection that blew up in February. STAT News reported that Vinay Prasad, then the FDA’s head of biologics, overturned his own career staff and issued a rare refusal-to-file notice because Moderna had not used an adjuvanted or high-dose comparator in the older group. His decision was reversed two weeks later after public disclosure, and he left the agency at the end of April. The regulatory dispute ended. The scientific objection was never answered.
What the trial tested was mRNA-1010 against a standard-dose shot, in everyone 50 and older together. It did not test mRNA-1010 against the high-dose or adjuvanted vaccines, and it did not report whether the benefit held up in the oldest patients on their own.
Both things can be true here: the mRNA platform is a real advance, as I noted when this trial first beat standard flu shots, and the specific claim for seniors is unproven while the high-dose shot keeps looking better than expected. An FDA advisory panel voted unanimously in June that the benefits outweigh the risks, and Flor Munoz-Rivas of Baylor College of Medicine told that meeting the studies “have very clear results that are very robust.” The manufacturing case is strong too: mRNA can be made fast enough to update strains closer to flu season, which also matters for pandemic preparedness.
What it means for you
What the trial showed, in adults 50 and older, is that this shot prevented more confirmed flu than a standard-dose shot. The benefit over a standard shot is real but modest in absolute terms, and expect a sorer arm and a rougher day or two than you are used to.
The trial makes only one comparison, against a licensed standard-dose shot, so it tells you nothing about how this vaccine stacks up against any other flu shot you may have had. Sticking with what you got last year is a defensible choice.
The question worth asking your doctor: has this been compared head to head against the high-dose shot for preventing flu in people my age? Today the answer is no.
What has not changed is that the biggest risk is skipping the shot entirely.