Messenger RNA (mRNA) influenza vaccines are opening a new chapter in flu prevention. Their significance lies in more than the use of a different technology. Available studies suggest that they can improve protection against influenza illness and promote an immune response capable of recognising a wider range of influenza viruses. These are related but distinct potential advantages, and it is important to distinguish carefully between what has been demonstrated and what remains under investigation.
In 2026, mRNA technology took a significant step forward in influenza prevention. On 5 August, the United States Food and Drug Administration (FDA) approved mFLUSIVA, developed by Moderna and known during development as mRNA-1010, for adults aged 50 and over. The FDA granted traditional approval for adults aged 50–64 and accelerated approval for those aged 65 and over. For the older age group, the accelerated approval requires confirmation of clinical benefit in a further study.
In the European Union, the European Commission authorised mCombriax on 20 April 2026. This mRNA vaccine combines protection against influenza and COVID-19 and is intended for adults aged 50 and over. Although the two products use the same technological platform, they are different vaccines and must be assessed on the evidence from their respective studies.
To understand the significance of these developments, we need to consider a challenge that has shaped influenza prevention for decades. Our immune defences can learn to recognise the virus, but the virus itself changes over time.
Why Influenza Vaccines Need Updating: Influenza viruses accumulate genetic changes as they circulate. Some of these changes affect proteins on their surface, which are recognised by many of our antibodies. When they alter the regions targeted by those antibodies, immune defences acquired through previous infections or vaccinations may become less effective at recognising the virus. This gradual process is known as antigenic drift.
Antibodies are proteins that bind to particular structures on an infectious agent. One way to picture this is as the recognition of a specific shape. If that shape changes, some antibodies may remain effective, while others become less so. This does not mean that all protection disappears, but it may diminish.
For this reason, the composition of influenza vaccines is reviewed regularly. Selecting the strains, manufacturing the doses and distributing them all take time. If the viruses that eventually predominate differ from those anticipated, the match between the vaccine and circulating viruses may be less favourable. This is one of the limitations that newer technologies seek to address.
mRNA vaccines offer two complementary possibilities. First, they may provide greater flexibility in updating vaccine formulations and manufacturing them. Second, they could broaden the immune response, making protection less dependent on an exact match between the viruses represented in the vaccine and those circulating in the community. This second possibility has attracted particular interest in recent research.
What an mRNA Vaccine Does: Messenger RNA carries temporary instructions for making proteins. In these vaccines, it enables some cells to produce selected viral proteins, which the immune system recognises as foreign. This initiates the process of immune learning without the need to administer the whole virus. The mRNA is subsequently broken down by the body.
In mRNA-1010, the instructions enable cells to produce haemagglutinin, a protein on the surface of influenza viruses that is targeted by many antibodies. The formulation evaluated in the large clinical efficacy trial contained instructions for producing haemagglutinins corresponding to three influenza strains selected for that season.
The vaccine does not supply ready-made immune defences. Instead, it provides instructions that allow the body to produce the proteins needed to trigger an immune response. The crucial questions concern the quality of that response, how long it lasts and the extent to which it enables the immune system to recognise different influenza viruses.
A Study of How Immune Defences Learn: Research published on 15 June 2026 in Nature Immunology, led by scientists at Washington University in St Louis and collaborators at other institutions, examined how the immune system responded to an mRNA influenza vaccine and a conventional vaccine. Its purpose was not to measure directly how many people developed influenza, but to understand what happened within their immune defences after vaccination.
This observational study included 75 healthy adults aged 20–50. Thirty-eight received an experimental four-component formulation of mRNA-1010, while 37 received Fluarix, a conventional vaccine made from inactivated, split influenza viruses. The research covered two consecutive influenza seasons, 2022–2023 and 2023–2024. The experimental four-component formulation should not be confused with the three-component formulation used in the subsequent clinical efficacy trial.
Overall, the researchers observed stronger antibody responses and higher frequencies of memory B cells among those who received the mRNA vaccine. Memory B cells retain information about previously recognised targets and help organise a more rapid response upon re-exposure. However, one of the most interesting findings came from examining lymph nodes in a subgroup of participants.
Lymph Nodes, Where the Immune Response Is Refined: Structures called germinal centres can form within lymph nodes during an immune response. Here, B cells multiply and undergo changes that affect how they recognise their targets. A process of selection favours cells whose antibodies bind more effectively to the relevant antigens.
A useful comparison is a workshop in which different tools are tested and refined. The analogy has an important limitation. Cells do not know which tool they need, nor do they act with conscious intent. Variations arise, and biological selection mechanisms allow some cells to thrive more successfully than others.
This process can improve antibody recognition and help shape the pool of memory cells. An immune response therefore cannot be assessed solely by its initial strength. How it develops, and what resources it leaves in place for the future, also matter.
In the subgroup whose lymph nodes were sampled, five of the thirteen participants who received the mRNA vaccine still showed influenza-specific germinal centre responses 26 weeks after vaccination. No equivalent persistence was detected in any of the fifteen participants who received the conventional vaccine. The number of participants in this subgroup was small, but the finding offers an important clue to how the immune response might be broadened and sustained.
It is worth being precise about what this means. The finding indicates that an immune process involving the selection and refinement of B cells was still active approximately six months after vaccination in some participants. It does not mean that the mRNA remained intact for that length of time, nor does it establish how long protection against illness lasted.
Producing More Antibodies Is Not Enough: Producing large quantities of antibodies can be useful, but their value also depends on what they recognise. If many target a region of the virus that changes readily, their usefulness may decline as new variants emerge. A more diverse repertoire, by contrast, may provide more opportunities to continue recognising related viruses.
In this study, antibodies from participants who received the mRNA vaccine showed broader binding to different influenza variants, including some with substantial differences in the structures recognised by the immune system. This broader recognition was observed during follow-up, which extended to six months.
The central concept is breadth of response. The aim is not simply to react more strongly to the anticipated virus, but to recognise a wider range of related viruses.
However, recognition measured in the laboratory does not automatically translate into clinical protection. Demonstrating that antibodies bind to different variants is one thing; showing that people experience fewer infections, hospital admissions or complications is another. Immunological studies help explain biological mechanisms, while clinical trials assess their consequences for health.
What Happened When Researchers Counted Influenza Cases: Clinical evidence comes from a separate study published in May 2026 in The New England Journal of Medicine. It enrolled 40,703 adults aged 50 and over, who were randomly assigned to receive either mRNA-1010 or a licensed standard-dose influenza vaccine. The primary objective was to compare the incidence of protocol-defined influenza-like illness confirmed by a molecular test.
The primary analysis recorded 411 cases among 20,179 participants in the mRNA group and 557 among 20,124 participants in the comparison group. These figures correspond to approximately 2.0% and 2.8%, respectively. The estimated relative vaccine efficacy was 26.6% in favour of mRNA-1010, with a 95% confidence interval of 16.7% to 35.4%. This interval conveys the statistical uncertainty surrounding the estimate and helps indicate its precision.
The figure of 26.6% can be misleading without context. It does not mean that the vaccine protected only 26.6% of its recipients, nor that it added 26.6 percentage points of protection. It means that the incidence of the influenza outcome defined in the trial was 26.6% lower in the mRNA group than in the group that received the comparison vaccine.
A more intuitive approach is to express the results per thousand people. Using the rounded trial proportions, there were about twenty cases per thousand participants who received the mRNA vaccine and about twenty-eight per thousand who received the comparison vaccine. The difference was therefore approximately eight fewer cases per thousand vaccinated participants during the study period. Both groups were vaccinated; the new vaccine was not compared with no vaccination.
The choice of comparator also matters. The trial demonstrated an advantage over a standard-dose vaccine. On its own, it does not establish that mRNA-1010 is superior to every alternative in every age group. For people aged 65 and over, the regulatory assessment also considered antibody-response data comparing mRNA-1010 with a high-dose vaccine. Accelerated approval in this age group requires confirmation of clinical benefit in a further study.
The immunological study and the clinical trial addressed different questions and examined different age groups. Their results are complementary, but they do not establish that persistent germinal centre activity was, by itself, responsible for the greater clinical efficacy observed in the trial.
Greater Efficacy Must Also Be Weighed Against Tolerability: In the clinical trial, solicited reactions following vaccination were more frequent in the mRNA group. Injection-site pain occurred in 65.8% of recipients, compared with 29.8% in the comparison group. Fatigue, headache and muscle aches were also more common. Most of these reactions were mild or moderate and temporary.
Serious adverse events were reported in 2.2% of participants in the mRNA group and 1.9% in the comparison group. It is important to distinguish between a health problem that occurs during follow-up and an effect caused by the vaccine. They are not equivalent. Investigators considered three events in the mRNA group and two in the comparison group to be related to vaccination.
A rigorous assessment of a vaccine must bring together efficacy, tolerability and monitoring for possible rare adverse effects. Improvement in one area does not remove the need to examine the others.
What the Combined Influenza and COVID-19 Vaccine Adds: mCombriax combines, in a single injection, mRNA instructions for producing proteins from influenza viruses and SARS-CoV-2, the virus that causes COVID-19. It does not contain the viruses themselves and cannot cause influenza or COVID-19.
According to the European Medicines Agency’s assessment, the main study, involving more than 8,000 people aged 50 and over, showed antibody responses comparable to those achieved by administering licensed vaccines against both diseases at the same visit. This evidence supported its authorisation, but it does not establish that the combined vaccine is superior to all alternatives in preventing hospital admissions, complications or death.
Its defining feature is that it brings both vaccinations together in one product. Results obtained with mRNA-1010 should not automatically be attributed to mCombriax, because each formulation has its own composition, dosing and supporting evidence. European authorisation also does not mean that availability or inclusion in vaccination programmes will be identical across countries.
An Important Advance, but Not Yet a Universal Vaccine: These findings bring research closer to a long-standing goal: influenza vaccines whose protection depends less on accurately anticipating the strains that will circulate each season. Prolonged selection within B cells and a broader antibody repertoire could help towards that goal. However, the findings do not demonstrate that a universal influenza vaccine already exists.
Several questions remain. Researchers still need to establish how long the clinical advantage lasts, how consistently it is observed across successive seasons and how far broader recognition in the laboratory translates into less illness when circulating viruses differ from those represented in the vaccine. Comparisons with the most appropriate alternatives for each population group will also be important.
Perhaps the most thought-provoking contribution of this research is a shift in perspective. Counting antibodies is not enough; we also need to understand what they recognise, how the response develops and what immune memory remains. Against a changing virus, the aim is not merely to provoke a strong response, but to prepare immune defences capable of recognising a wider range of variants.
mRNA influenza vaccines have demonstrated a clinical advantage over a standard-dose vaccine in a trial involving adults aged 50 and over. The immunological study has also provided evidence of broader antibody binding to influenza variants and documented persistent germinal centre responses in some participants. These are complementary and promising findings, but they do not yet establish universal protection or determine how long the potential clinical advantage will last. The full significance of this advance will need to be clarified through further studies and the experience gained from its use.
Today’s research is tomorrow’s therapy