The flu vaccines currently approved and available in the United States do not contain mRNA. All flu shots on the market today are made using one of three older technologies: growing the virus in eggs, growing it in animal cells, or manufacturing a key viral protein directly through recombinant methods. None of these approaches involve mRNA. That said, the question is understandable given how prominent mRNA technology became during the COVID-19 pandemic, and the landscape is shifting: several mRNA-based flu vaccines are now in advanced clinical trials, with some in phase 3 testing.
What Is Actually in Today’s Flu Vaccines
The CDC identifies three production methods behind every flu vaccine currently licensed for use in the United States: egg-based manufacturing, cell-culture-based manufacturing, and recombinant manufacturing.1Centers for Disease Control and Prevention. How Influenza (Flu) Vaccines Are Made – Section: Key points The vast majority of flu doses given each year come from the egg-based process, which has been the backbone of flu vaccine production for decades. In this method, candidate vaccine viruses are injected into fertilized chicken eggs, allowed to replicate, then harvested, purified, and either inactivated (killed) or attenuated (weakened). The result is a vaccine that contains pieces of the flu virus itself, not genetic instructions for making those pieces.
Cell-culture-based flu vaccines work similarly but skip the eggs, instead growing the virus in mammalian cell lines. Recombinant flu vaccines take yet another approach: they use an insect virus to produce large quantities of a flu surface protein called hemagglutinin, then package that protein into a vaccine. All three methods deliver the finished viral protein or inactivated virus to your immune system directly. None of them rely on your own cells to build the protein from a genetic template, which is the defining feature of mRNA vaccines.
Why the Confusion Exists
The COVID-19 vaccines from Pfizer-BioNTech and Moderna introduced mRNA technology to hundreds of millions of people in a remarkably short time. Before 2020, most people had never heard the term “mRNA vaccine.” After 2021, it was hard to avoid. That sudden ubiquity left a lot of people unsure which vaccines use the technology and which do not. When you hear about a new flu shot each fall, it is reasonable to wonder whether it has quietly switched to the same platform.
It has not. But the confusion is reinforced by the fact that mRNA flu vaccines are genuinely in development and regularly appear in news headlines. Seeing “mRNA” and “flu” in the same sentence can easily give the impression that these products are already on pharmacy shelves. They are not, at least not yet.
mRNA Flu Vaccines in Clinical Trials
Several pharmaceutical companies are testing mRNA-based flu vaccines in humans, and at least one candidate has reached phase 3 trials. Moderna’s mRNA-1010 is a quadrivalent (four-strain) mRNA flu vaccine that has been tested in a large, three-part phase 3 clinical trial comparing its safety and immune response against licensed standard-dose and high-dose flu vaccines in adults aged 18 and older.2Elsevier / Vaccine. A phase 3 randomized safety and immunogenicity trial of mRNA-1010 seasonal influenza vaccine in adults Phase 3 is the final stage of testing before a company can apply for regulatory approval, so these products are not in some distant, speculative phase of research. They are being directly compared to the flu shots people already get.
Whether mRNA-1010 or any competing mRNA flu candidate will ultimately be approved depends on the trial results and regulatory review. But the trajectory is clear: mRNA flu vaccines are being built, tested, and evaluated in the same rigorous framework that every other vaccine goes through. If one is approved, it would be offered alongside or as an alternative to the existing egg-based, cell-based, and recombinant options.
How an mRNA Flu Vaccine Would Differ from Current Shots
Traditional flu vaccines hand your immune system the finished product: either a killed virus or a purified protein from the virus’s surface. Your immune cells recognize these foreign materials, learn to target them, and build memory so they can respond quickly if the real virus shows up later. The heavy lifting of making the protein happens in a factory, not in your body.
An mRNA flu vaccine flips that step. Instead of delivering the protein directly, it delivers a strip of messenger RNA, a genetic instruction set, wrapped in a tiny fat bubble called a lipid nanoparticle. Once that package enters your cells, your cells read the mRNA instructions and produce the flu protein themselves. Research on avian influenza mRNA vaccines has shown that once the mRNA-lipid nanoparticle enters a cell, the cell produces the hemagglutinin protein, and fragments of that protein get displayed on the cell’s surface in a way that activates immune cells, triggering both antibody and cellular immune responses.3Springer Nature. Avian influenza mRNA vaccine encoding hemagglutinin provides complete protection against divergent H5N1 viruses in specific-pathogen-free chickens – Section: Discussion The mRNA itself is fragile and gets broken down by the cell within days. It does not enter the cell’s nucleus and does not alter DNA.
For the person getting the shot, the practical experience would be similar: a needle in the arm, possible soreness at the injection site, and the usual mild side effects like fatigue or a low-grade fever. The difference is happening at the molecular level, in how your immune system first encounters the flu protein.
Why Researchers Are Pursuing mRNA for Flu
If the existing flu vaccines work, why bother developing mRNA versions? The answer comes down to speed, flexibility, and the persistent problem of strain mismatch. Every year, public health officials have to predict which flu strains will dominate the coming season and then manufacture vaccines months in advance. The egg-based process is slow. Candidate viruses sometimes grow poorly in eggs, and the long production timeline means the strain selection has to happen far ahead of when the vaccine is actually needed. If the virus drifts between the time strains are chosen and when flu season peaks, the vaccine can end up being a poor match, reducing its effectiveness.
mRNA vaccines follow a simpler and more reproducible manufacturing process that uses the same raw materials regardless of which viral protein is being encoded. This could allow strain selection to happen closer to the start of flu season, reducing the risk that the virus changes after the vaccine has already been locked in.4Taylor & Francis. Influenza seasonal influenza vaccine performance and the potential benefits of mRNA vaccines – Section: Rapid, scalable manufacturing process In principle, updating an mRNA vaccine for a new strain means swapping in a different genetic sequence rather than restarting the biological process of growing virus in eggs or cells. That is a meaningful advantage when you are racing against a virus that mutates constantly.
There are also questions about whether the immune response generated by mRNA vaccines could be qualitatively different from what traditional vaccines produce. Because the protein is made inside your own cells rather than injected pre-formed, the immune system encounters it in a way that may activate different arms of the immune response. Whether that translates to better real-world protection against flu is exactly what the ongoing trials are designed to answer.
Combination Vaccines on the Horizon
One of the more interesting developments in this space is the push toward combination mRNA vaccines that protect against both flu and COVID-19 in a single shot. The logic is straightforward: both viruses circulate in the fall and winter, both require regular vaccination updates, and both can be targeted using the same mRNA platform. If you could roll two vaccines into one injection, that would simplify the annual immunization routine considerably.
Preclinical work on combination influenza and COVID-19 mRNA vaccines is already producing encouraging results. One research group has developed a next-generation seasonal flu vaccine design that, when tested alone or as part of a combination flu/COVID-19 mRNA vaccine, generated antibody responses significantly higher than those from Fluzone HD, a licensed high-dose inactivated flu vaccine, across all 2024/2025 seasonal flu strains.5MDPI Vaccines. Development of an Influenza/COVID-19 Combination mRNA Vaccine Containing a Novel Multivalent Antigen Design That Enhances Immunogenicity of Influenza Virus B Hemagglutinins – Section: 3.3. Application of Dumbbell Antigens to Influenza/COVID-19 Combination mRNA Vaccines These are preclinical findings, meaning they have not yet been confirmed in human trials, but they illustrate how versatile the mRNA platform is. You can encode multiple antigens from different viruses on the same set of mRNA strands and wrap them all in one lipid nanoparticle package.
If combination mRNA vaccines eventually reach approval, the annual decision about getting a flu shot and a COVID booster could collapse into a single appointment with a single injection. That prospect is driving significant investment from multiple vaccine manufacturers.
What This Means if You Are Getting a Flu Shot This Year
If you walk into a pharmacy or clinic today and ask for a flu vaccine, you will receive one of the three established types: egg-based, cell-based, or recombinant. None contain mRNA. You do not need to ask for a special version or worry about accidentally receiving an mRNA flu vaccine, because none are available outside of clinical trials. If you are specifically interested in or specifically want to avoid mRNA technology, the current flu vaccine lineup is irrelevant to that preference either way.
That could change in coming years if any of the mRNA flu candidates clear regulatory review. At that point, mRNA flu vaccines would presumably be listed as a distinct option, much like the current distinction between standard-dose and high-dose flu shots or between egg-based and recombinant products. Pharmacists already navigate multiple flu vaccine options each season, and adding an mRNA version would simply extend that menu.
The Egg Allergy Connection Worth Knowing About
One practical angle that rarely gets mentioned in the mRNA conversation is the egg allergy question. Because most flu vaccines are grown in eggs, people with egg allergies have historically had to navigate special considerations around flu vaccination. Cell-based and recombinant flu vaccines were partly developed to address this concern. mRNA flu vaccines, if approved, would offer yet another egg-free option, since the manufacturing process does not involve eggs at any stage. For the small number of people with severe egg allergies who find the current egg-free options limited or unavailable, an mRNA flu vaccine would widen the field.
How mRNA Flu Vaccines Relate to Bird Flu Preparedness
The same mRNA technology being tested for seasonal flu is also being explored as a tool against avian influenza, including H5N1 strains that have raised pandemic concerns. Research on mRNA vaccines encoding the hemagglutinin protein from H5N1 has shown strong protective responses in animal models, with one study demonstrating complete protection in chickens against divergent H5N1 viruses.3Springer Nature. Avian influenza mRNA vaccine encoding hemagglutinin provides complete protection against divergent H5N1 viruses in specific-pathogen-free chickens – Section: Discussion
The relevance here is speed. If an avian flu strain ever began spreading efficiently between humans, the world would need a vaccine fast. The traditional egg-based manufacturing process is poorly suited to pandemic-speed production, partly because the very eggs used to grow the vaccine could become scarce if poultry flocks are being devastated by the same virus. mRNA production sidesteps that dependency entirely. You need the genetic sequence of the target protein, the synthetic raw materials to build the mRNA, and the lipid nanoparticles to wrap it in. No eggs, no cell cultures, no dependency on biological substrates that a pandemic could disrupt.
This is one of the less-discussed but strategically important reasons governments and companies are investing in mRNA flu technology. Even if mRNA seasonal flu vaccines turn out to be only roughly equivalent to existing options in normal years, their value as a rapid-response platform during a pandemic influenza event could be enormous. The COVID-19 experience demonstrated that mRNA vaccines can go from sequence identification to clinical-trial doses in a matter of weeks, a timeline that egg-based manufacturing simply cannot match.
Common Misconceptions About mRNA and Flu Shots
A few specific misunderstandings circulate widely enough to be worth addressing directly. The first is the belief that mRNA has been “snuck into” the regular flu shot without public disclosure. Vaccine ingredients are public information, listed on FDA-approved package inserts for every licensed product. No currently approved flu vaccine contains mRNA, and if one were approved, it would be labeled as such and listed as a distinct product.
The second is the idea that all vaccines are moving to mRNA and traditional options will disappear. There is no indication of that. Egg-based flu vaccines remain the workhorse of global production, and cell-based and recombinant vaccines have carved out their own roles. mRNA vaccines, if approved for flu, would be added to the menu rather than replacing what already exists. Different platforms have different strengths, and public health systems benefit from having multiple manufacturing methods available, especially during supply disruptions.
A third misconception is that mRNA vaccines are entirely new and untested. The COVID-19 vaccines were the first mRNA products to receive widespread use, but the underlying research stretches back decades. The speed of COVID vaccine development reflected years of prior work on mRNA delivery systems and lipid nanoparticle engineering, not a rushed invention. mRNA flu vaccine candidates are building on that foundation, with the additional advantage of large-scale safety data from billions of COVID-19 mRNA doses administered worldwide. That does not guarantee any particular mRNA flu vaccine will be safe and effective, which is what clinical trials are for, but it does mean the platform itself is no longer experimental in any meaningful sense.