What Is an mRNA Flu Vaccine? How It Works and Canada’s New Approval, November 2026

Verified November 7, 2026, at 04:03 UTC (UTC+00:00).

An mRNA flu vaccine gives the body temporary instructions for making an influenza protein, helping the immune system recognize the virus before an infection occurs. The approach has become relevant in Canada: on November 5, 2026, Moderna announced that Health Canada had authorized its mRNA seasonal flu vaccine, mFLUSIVA, for adults ages 50 and older.

Authorization does not mean the vaccine is immediately available. Moderna has not announced a Canadian launch date, and a company spokesperson told The Canadian Press that the new vaccine would not reach pharmacies in time for the 2026–2027 respiratory virus season. Canadians can still get an age-appropriate flu vaccine available this season. Read Moderna’s authorization announcement and The Canadian Press report on availability.

Destaques

• mRNA provides temporary instructions that help cells make a flu protein and train the immune system.
• Canada has authorized mFLUSIVA for adults 50 and older, but a Canadian launch date has not been announced.
• In a large trial, mFLUSIVA produced fewer flu cases than one standard-dose flu vaccine; that does not establish that it is better than every flu vaccine.
• Canada recommends an annual, age-appropriate flu vaccine for people six months and older who have no contraindication.

What is an mRNA flu vaccine?

Messenger RNA, or mRNA, is a molecule that carries instructions cells can use to make proteins. An mRNA flu vaccine packages instructions for making selected influenza proteins in tiny fat particles called lipid nanoparticles. These particles help deliver the instructions into cells after vaccination.

The goal is familiar: prepare the immune system to respond to influenza. The difference is how the immune system encounters its target. Rather than supplying an inactivated flu virus or its components directly, an mRNA vaccine supplies instructions that let the body make a viral protein for a short time.

Health Canada also authorized Moderna’s mCOFLU, a separate combination mRNA vaccine for influenza and COVID-19, for adults 50 and older. An authorization for a particular product and age group should not be confused with availability or a recommendation that everyone receive it.

How does an mRNA flu vaccine work?

After the injection, some cells take up the lipid particles and use the mRNA instructions to make an influenza protein, such as hemagglutinin, a protein found on the virus’s surface. The immune system recognizes that protein as foreign and develops a response, including antibodies and immune memory. If the vaccinated person later encounters a related flu virus, that preparation can help the body respond.

The vaccine does not contain a complete live influenza virus and cannot give someone flu. The mRNA is temporary: cells break it down after using it. It does not change a person’s DNA. Health Canada explains the same basic mechanism in its guide to mRNA vaccines, which describes COVID-19 vaccines using the platform.

How is an mRNA flu vaccine different from a regular flu shot?

Most conventional flu shots used in Canada are inactivated vaccines: they contain killed virus or viral components that cannot cause influenza. Some are made using eggs, while another uses mammalian cell culture. Canada also authorizes a nasal spray containing weakened live influenza viruses for eligible people. An mRNA flu shot instead delivers genetic instructions for making selected flu proteins.

The approaches share the same purpose, but individual products differ in age eligibility, ingredients, evidence and availability. Some conventional vaccines are designed for older adults, including high-dose and adjuvanted options. An adjuvant is an ingredient added to strengthen the immune response. The Canadian Immunization Guide describes the flu vaccine types authorized in Canada; its list may take time to reflect a very recent authorization.

Is the mRNA flu vaccine more effective?

In a phase 3 trial involving approximately 40,800 adults ages 50 and older, Moderna reported that mFLUSIVA had 26.6% greater relative efficacy against the study’s laboratory-confirmed, protocol-defined influenza illness than a licensed standard-dose inactivated flu vaccine. In practical terms, the measured flu illness occurred less often in the mRNA vaccine group than in that comparator group.

That figure is a relative comparison, not a claim that the vaccine prevents 26.6% of all flu infections or that it is 26.6 percentage points more effective. The study compared one mRNA product with one standard-dose vaccine in a particular population and season. It does not prove superiority over every available flu vaccine, including high-dose or adjuvanted products for older adults. Moderna’s phase 3 results announcement explains the comparison.

What side effects can an mRNA flu vaccine cause?

In the mFLUSIVA trial, Moderna reported injection-site pain, fatigue, headache and muscle aches among the most common reactions; most solicited reactions were mild. Side effects and precautions can vary by product. A serious allergic reaction after vaccination requires urgent medical care. Before vaccination, tell a health care professional about a previous severe allergic reaction to a vaccine or one of its ingredients, and discuss any other health concerns.

Regulators assess evidence on quality, safety and effectiveness before authorization, and safety monitoring continues afterward. A large trial can identify many reactions, but continued monitoring is important for detecting very rare events.

Will mRNA technology change annual flu vaccination?

Potentially, but the practical benefit will depend on future evidence, manufacturing and access. An mRNA sequence can be redesigned for different targets, which may help vaccine developers respond to changing viruses. Faster design alone does not guarantee a better match or eliminate the time needed for testing, regulatory review, production and distribution.

Annual vaccination remains important because flu viruses change and protection can decrease over time. For 2026–2027, Canada’s National Advisory Committee on Immunization recommends offering an influenza vaccine annually to everyone six months and older without a contraindication. It recommends a high-dose or adjuvanted inactivated vaccine for adults 65 and older when available; if a preferred option is unavailable, an age-appropriate vaccine should be used. Local availability varies, so ask a pharmacist, health care professional or public health authority about options. See the 2026–2027 Canadian recommendations.

FAQ

Can an mRNA flu vaccine give you the flu?

No. It does not contain a complete live influenza virus. Temporary reactions such as fatigue or muscle aches can occur after vaccination.

Does an mRNA flu vaccine change your DNA?

No. The mRNA provides temporary protein-making instructions and is broken down by cells; it does not change DNA.

Should I wait for an mRNA flu vaccine?

Its Canadian launch date has not been announced. For protection this season, consult a health care professional or local public health authority about an age-appropriate flu vaccine that is available now.