This new mRNA vaccine could better protect against the flu

​​​Traditional flu vaccines have been around for more than 80 years. Their efficacy, however, fluctuates year to year, which means Canadians are still falling ill at high rates. ​​An average of more than 10,000 hospitalizations and hundreds of deaths occur in Canada every year related to the flu.

In Quebec alone, the 2024 influenza season is estimated to have cost $655 million – $107 million in direct medical costs and the rest split between lost productivity and premature mortality.

But a significant development is on its way. An mRNA influenza vaccine that is 27 per cent more effective than the traditional flu vaccine has been approved in the United States and is under regulatory review by Health Canada. Developed by Moderna, the vaccine, called mFlusiva, deploys the same mRNA technology used in ​​COVID-19 vaccines.

​​​Currently, most flu vaccines are made by injecting a small amount of inactivated flu virus into a fertilized chicken egg and allowing it to replicate over a few days. That process takes time to produce vaccines en masse.

“They have to make their best guess as to what influenza strains will be circulating six months from now and then manufacture the vaccine,” explains Dr. Isaac Bogoch, an infectious diseases specialist and general internist at Toronto General Hospital. “The circulating influenza can change and mutate and sometimes six months later, there might be slightly different strains of flu circulating, such that the vaccine is not as good a match as we’d like.” On top of that, the virus can also mutate inside the egg while it’s replicating. “That’s why there’s a significant range of vaccine effectiveness year after year,” Bogoch says.

But mRNA vaccines work differently. While an injection of weakened virus triggers an immune response and produces antibodies, mRNA vaccines teach cells how to make a protein that triggers an immune response instead. “You can mass produce this much faster,” Bogoch says. “Instead of six months, you can shorten that to as little as two, maybe three months.”

Another advantage of mRNA is that there’s no chance of mutation during vaccine production. This allows the mRNA to be much more precise, leading to better protection against influenza. ​​A May 2026 clinical trial of more than 40,000 participants aged 50 and older showed that 2.8 per cent of those who received the traditional flu vaccine reported “influenza-like illness,” while only two per cent of those who received the mRNA version were stricken. These differences may be slight, but when applied to the scale of millions, the impact is significant. “At a population level, that means fewer people getting sick,” says Bogoch. “That could lead to fewer absences from work, fewer hospitalizations, fewer deaths.” 

Two Canadians played outsized roles in getting us here. Derrick Rossi, a Toronto-born stem cell biologist, discovered in 2008 that modified mRNA could be used to direct cells to make new proteins – the finding that led him to co-found Moderna. And the delivery system that makes any of it work in the body, lipid nanoparticles that shuttle mRNA into cells, took University of British Columbia biochemist Pieter Cullis more than 40 years to develop.

But before it gets into Canadians’ arms, the new mRNA flu vaccine will have to pass through a few steps. First, Health Canada needs to approve it. It was submitted in late 2025, and the agency’s standard review typically takes around 300 days, which would put a decision sometime this year. From there, each province and territory ​​​​decides how to make it available, which means access will look different across the country.

Timothy Caulfield, a professor in the Faculty of Law and the School of Public Health at the University of Alberta, expects that variation to be wide, citing differences in how the ​COVID-19​ vaccine is currently being made available: some provinces are “bending over backwards” to improve access, he says, making shots free and available at pharmacies and clinics.​​ Others are moving the other way: “Generally, in Alberta, you have to pay for the COVID vaccine,” he says. ​​​​“They put barriers in place to access it.” Alberta’s government says the policy is about reducing vaccine waste, but public health experts warn it will create exactly the kind of access barrier Caulfield describes. So, while the new mRNA flu vaccine is likely to be available to much of the country by next winter, how easily – and how affordably – will depend on the province.

Uptake is the other variable. ​​Canada’s own vaccination coverage has been falling. Senior uptake is now around 64 per cent, down from 73 per cent two seasons ago and well below the 80 per cent national target, while only 34 per cent of adults aged 18–64 with chronic conditions get a flu shot, down from 44 per cent. Caulfield thinks misinformation about mRNA could further dampen the public’s willingness to roll up their sleeves. Unlike older vaccine technology, mRNA vaccines are new enough that many people say they simply don’t know enough to judge them – a gap that’s often filled by persistent false claims, like the idea that mRNA vaccines alter your DNA, along with lingering associations with the unusually fast emergency timeline of the ​​COVID-19 rollout.

Even people who trust the science may hesitate over side effects; pain, fatigue and headaches are somewhat more common with mRNA vaccines, though they typically last only a few days. Rolling out any vaccine​​ at national scale can also reveal rare side effects that trials weren’t large enough to catch. None of these is a roadblock so much as a reason the rollout will be uneven – faster in some provinces, slower in others.

But the direction is set. As the new mRNA flu vaccine clears approval and reaches pharmacies, it stands to give Canada’s health-care system a meaningful reprieve – fewer sick Canadians, fewer hospitalizations and fewer frail seniors who never make it back to independent living after a bad flu season. “Anything that can be done to alleviate pressure on the health-care system,” Bogoch says, “is clearly a good intervention.”