An expert committee at the US Food and Drug Administration (FDA) unanimously recommended approving Moderna's new flu vaccine, a move that could signal the start of a new era in preventing the seasonal illness.
The vaccine, intended for people 50 and older, is based on mRNA technology and was found in an advanced trial to be more effective than a standard flu shot.
The FDA's vaccine advisory committee voted unanimously on Thursday in favor of the new Moderna vaccine, called mFlusiva, after reviewing its safety and efficacy data. If it receives final approval, it will be the world's first mRNA-based flu vaccine.
The recommendation was made for two age groups: people 50 to 64 and people 65 and older. For the older group, in which flu complications are more common and more severe, the committee asked Moderna to carry out an additional study after the vaccine enters the market.
The main figure driving the discussion was the vaccine's effectiveness compared with a standard flu shot. In a late-stage trial, Moderna's vaccine was found to be about 27% more effective than the older shot in preventing influenza.
That is a significant gap in a field where vaccine effectiveness varies greatly from season to season, depending on how well the vaccine matches the virus strains actually circulating in the population.
Flu is often seen as a routine winter illness, but among older adults, people with chronic illnesses, pregnant women, and young children, it can cause severe complications. Every year, thousands are hospitalized in Israel because of flu and its complications, including pneumonia, worsening heart and lung disease, respiratory failure, and death.
People 65 and older account for most severe hospitalizations, which is why the discussion over a more effective vaccine for older age groups has broad medical and public importance.
Traditional flu vaccines are produced using long-established methods, some of which are based on fertilized eggs or cell cultures.
Where does mRNA come in?
One of their main limitations is timing; manufacturers must choose months in advance which flu strains will be included in the seasonal vaccine. During the months before winter begins, the virus may change, and the match between the vaccine and the active strains can weaken.
This is where mRNA technology comes in. Instead of growing the virus or its parts through lengthy biological methods, the vaccine uses a short segment of genetic code that instructs the body's cells to produce a protein similar to a component of the flu virus.
The immune system recognizes that protein, mounts an immune response against it, and is then expected to react more quickly if it is later exposed to the real virus. The genetic material in the vaccine breaks down in the body and does not remain there.
Moderna also has another possible advantage, speed of production. The company told the committee that it can move from selecting flu strains to distributing the vaccine within two to three months, compared with about six months in some traditional production methods.
In theory, that means the vaccine composition could be updated later in the year, closer to flu season, to better match the strains that are actually spreading.
The new vaccine was reported to have side effects similar to those known from other vaccines, including pain at the injection site, fatigue, muscle aches, and fever.
According to the data discussed by the committee, no unusual safety problems were identified that shifted the benefit-risk balance against the vaccine. Still, the call for additional research among people 65 and older reflects regulatory caution, mainly because the risk of severe flu is higher in that group and the standard for comparing vaccines is more complex.
Opens doors to new vaccines
If the vaccine is approved, it could open the door to a new generation of flu vaccines that can be updated more quickly. For health systems, that could be particularly important in seasons when flu strains change rapidly or when there is only a partial match between the seasonal vaccine and the active viruses.
The decision is also expected to affect the continued development of combination vaccines, including a one-shot vaccine against both flu and COVID-19. Moderna and other companies have been trying in recent years to develop combination vaccines that would make it easier for older adults and at-risk groups to receive broader protection in a single injection.
Approval of the new flu vaccine could strengthen confidence in that path, but it would also require continued monitoring of efficacy, safety, and public uptake.