How the technology used to make COVID-19 vaccines could improve flu shots

With flu season fast approaching, people who haven't been vaccinated against COVID-19 or qualify for a third dose can safely get shots to protect them against both illnesses in the same visit, say health experts.

They anticipate that in the future, by applying the latest advances in mRNA technology, it may be possible to vaccinate a person against COVID-19 and the seasonal flu with a single vaccine. 

That's because vaccine developers have been working on developing influenza vaccines using mRNA technology, the kind used in the Pfizer-BioNTech and Moderna COVID-19 vaccines, since before the pandemic, said Susy Hota, medical director of infection prevention and control at the University Health Network in Toronto. 

Several are already at the clinical trial stage.

No COVID-19 and flu combo vaccine is that far along. 

Hota says it would be incredibly convenient to leverage mRNA technology to better protect people against the flu.  

"What the future may hold is having one single, combined vaccine that addresses multiple infections that circulate at the same time. So that could be COVID 19 and influenza," she told Dr. Brian Goldman, host of CBC Radio's The Dose podcast.

"We're not there yet. But wouldn't that be nice, coming in for your one respiratory virus injection that will cover you for that season?" 

Flu viruses mutate frequently as they circulate around the world, Hota said. By the time scientists see what strains are taking off in the Southern Hemisphere and predict what to put in flu vaccines for people in the Northern Hemisphere, there could be mismatches.

On average, flu vaccines are about 40 to 60 per cent effective in protecting you from infection, Hota said. 

Since people infected with flu are at higher risk for having heart attacks and other cardiac problems than the general population, flu vaccinations save lives, she said.

"If we were to see too many COVID-19 and influenza patients coming to our hospitals, that could paralyze the system," she said.

Vaccine makers are trying to catch up with the mutating virus so that what's in their vials better matches the flu strains we might encounter from others who are coughing or perhaps talking a bit too close. 

That's where mRNA technology comes in. Experts say perhaps they could observe flu activity worldwide for a longer period and then take advantage of the speed of mRNA vaccine manufacturing to add circulating flu strains to vaccines in time to better protect the public.