Moderna messenger RNA flu shots could reshape Canadian immunization schedules by allowing health officials to select viral strains in June instead of February.
Canada’s flu season hit emergency room wait times in early November, pushing influenza-positive test rates to 12 percent according to the Ministry of Health. Health Canada approved two Moderna mRNA influenza vaccines in early November, covering both standalone flu protection and a combined flu-COVID-19 shot.
Traditional vaccine manufacturing requires the World Health Organization to select Northern Hemisphere influenza strains during a February meeting. That timeline makes it impossible to evaluate viral strains circulating in the Southern Hemisphere during Australia’s winter months, which begin in April.
"Our goal is simply to produce vaccines more quickly, but we can take advantage of that speed to improve the match with circulating viruses," said James Mansi, vice-president of medical affairs at Moderna Canada, told lapresse.ca.
Moderna’s mRNA technology allows the company to pick influenza strains as late as June. That three-to-four-month delay lets manufacturers observe actual strain evolution in the Southern Hemisphere.
"Gaining three or four months of observation in the Southern Hemisphere could be very useful," said Jesse Papenburg, a pediatric infectious disease specialist at the Montreal Children’s Hospital and chair of the Quebec Immunization Committee, told lapresse.ca.
Moderna’s new influenza vaccines will not be available in Canada this winter, according to Mansi.
Predicting Vaccine Effectiveness Remains Difficult
Last year’s traditional flu vaccine missed the mark on dominant circulating strains in the Northern Hemisphere. Despite that mismatch, overall vaccine effectiveness landed at 40 percent, matching historical averages.
"It is very difficult to predict influenza vaccine effectiveness, because we lack data," said Colin Russell, a microbiologist at the University of Amsterdam who published a study on the subject in 2025, told lapresse.ca.
Russell’s research indicates that moving strain selection later in the year could boost vaccine matching by 50 percent. His study points to the 2014-2015 flu season as a cautionary tale. Vaccine effectiveness dropped below 10 percent during that winter, while Canadian deaths surpassed 550 compared to the typical annual range of 250 to 350.
Avian Influenza H5N1 Monitoring Continues
"Getting vaccinated against seasonal flu does not improve protection against H5N1, but we saw antibodies, probably because of flu infections and vaccinations in previous years," said Andrés Finzi, a virologist at the CHUM research center and co-author of the study, told lapresse.ca. "If ever there was a human outbreak, a H5N1 vaccine would be worthwhile."
Questions about Moderna flu shots and seasonal protection
When will Moderna’s mRNA flu shots become available in Canada?
Health Canada approved the shots in early November, but the vaccines will not be distributed in Canada this winter.
Why does traditional flu vaccine manufacturing start in February?
The World Health Organization holds its Northern Hemisphere selection meeting in February to give traditional manufacturing facilities enough lead time to produce millions of doses before winter.
Does the seasonal flu shot protect against H5N1 avian influenza?
Seasonal influenza vaccination does not provide cross-protection against H5N1, though researchers have detected low levels of baseline antibodies in the population from past seasonal flu exposures.