After decades: A new flu vaccine has been approved that may change the rules of the game
The US Food and Drug Administration (FDA) has approved Moderna's Mfalusiva, the first seasonal flu vaccine based on mRNA technology. In a large-scale trial, the vaccine showed a 26.6% higher relative efficacy compared to a standard-dose flu vaccine.
A breakthrough in protection against winter illnesses: For the first time since seasonal flu vaccines were developed, the US Food and Drug Administration (FDA) has approved a vaccine using mRNA technology, the same platform used to create COVID-19 vaccines. The new vaccine, Moderna's Mfalusiva, was approved for individuals aged 50 and older after a trial involving more than 40,000 participants succeeded in reducing flu cases at a higher rate than a standard vaccine. The approval marks a new phase in the attempt to improve the response to a virus that changes rapidly and leads to hundreds of thousands of hospitalizations worldwide each year.
The approval was granted through two different pathways. For those aged 50 to 64, the FDA granted regular approval based on efficacy and safety results from the clinical trial. For those aged 65 and older, accelerated approval was granted, requiring Moderna to conduct an additional study to confirm the clinical benefit in the elderly population. This is not an emergency authorization, but a marketing approval accompanied by a requirement for continued monitoring and data collection.
The main study included 40,703 people aged 50 and older who were randomly assigned to receive the new vaccine or an approved standard-dose flu vaccine. In the Mfalusiva group, 411 confirmed flu cases were diagnosed, which is 2% of participants, compared to 557 cases, or 2.8%, among those who received the standard vaccine. After statistical analysis, the researchers determined that the relative efficacy of the new vaccine was 26.6% higher.
Mfalusiva is a vaccine targeted against two strains of influenza A and one strain from the influenza B family. Similar to the COVID-19 vaccines based on the same platform, it contains messenger RNA molecules wrapped in lipid particles. The molecules provide cells with temporary instructions to produce proteins similar to those on the surface of the flu virus. The immune system recognizes them, develops antibodies and memory cells, and is thus supposed to respond quickly in the event of exposure to the virus itself. The vaccine does not contain a live virus and cannot cause the flu.
One of the potential advantages of the technology is the shortening of the production process. Traditional flu vaccines are mostly produced by growing viruses in chicken eggs or cell cultures, a process that begins months before the winter season. Health organizations are required to choose the vaccine composition well in advance, while the virus may continue to change. Moderna claims that it is possible to move from strain selection to vaccine production within two to three months, compared to about half a year with some traditional production methods.
Shortening the timeline may allow for a later and more accurate match to the strains expected to spread, but it has not yet been proven that the theoretical advantage will lead to better clinical protection in every season. Flu viruses undergo frequent genetic changes, and even a vaccine created quickly may provide only partial protection if the changing strains are different from those selected for its composition.
Side effects were more common among recipients of the new vaccine. Pain at the injection site was reported by about 66% of Mfalusiva recipients compared to about 30% in the comparison group. Fatigue, headaches, muscle aches, and chills also appeared at a higher rate. Most reactions were mild to moderate and resolved within a few days. The rate of serious side effects that were not predefined was similar between the groups, and no new safety issue was identified in the trial that changed the benefit-risk balance.
In Israel, the vaccine has not yet been approved for use. The FDA approval applies at this stage only to the United States, and any local marketing will require registration and separate approval from the Ministry of Health. Even if it is submitted for approval in Israel, it will be necessary to examine its price, availability, its suitability for the composition of strains in the Northern Hemisphere, and its place alongside the high-dose vaccines already provided to the elderly population.
