White Coat, Black Art·The Dose

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

People can safely receive a dose of COVID-19 vaccine in one arm and a flu shot in the other during the same clinic visit, health experts say. Meanwhile, scientists are working on a way to combine them in a single jab.

In the future, protection from COVID-19 and the flu might be combined in a single shot, experts say

A woman wearing a medical mask holds a needle in preparation for an injection.
A student pharmacist prepares a flu shot in Los Angeles last October. Canada's flu and respiratory virus season tends to start in November. (Damian Dovarganes/The Associated Press)
Some experts fear this year's flu season will be severe - especially with the pandemic still raging in many parts of Canada. Dr. Brian Goldman speaks with Dr. Susy Hota, Medical Director for Infection Prevention and Control at University Health Network in Toronto, about the latest developments in flu vaccines.

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?" 

People get flu shots in Calgary last October. The vaccinations are available at pharmacies and primary care offices. (Leah Hennel/Alberta Health Services)

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.

Speed is of the essence to beat flu

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.

Dr. Susy Hota says getting two jabs at the same time to protect against COVID-19 and the flu is well worth it. (Craig Chivers/CBC)

Scott Halperin, a pediatric infectious diseases specialist and professor at Dalhousie University in Halifax, leads clinical trials for influenza and other vaccines at the Canadian Centre for Vaccinology. 

He says mRNA technology could likely accelerate the manufacturing of flu vaccines compared with the time-consuming approach of growing the virus in chicken eggs that's used today.

At least three companies say they're starting Phase 1 human safety trials of mRNA flu-only vaccines to check if the side-effects mirror those from conventional flu vaccines, such as a sore arm or fever. 

To eventually combine COVID-19 and flu protection in one jab, researchers first need to test that mRNA technology can be applied safely and effectively to influenza viruses. 

New technology brings better immunity

Moderna and Pfizer's mRNA vaccines for COVID-19 include the genetic instructions to make a modified spike protein from the virus. Once the vaccine is injected into the body, human cells use the instructions to make copies of the spike protein for the immune system to learn to recognize.

WATCH | Flu shots recommended amid COVID's 4th wave:

Doctors urging flu shots to prevent further health-care strain

1 year ago
Duration 3:30
Canadians are being urged to get flu shots as soon as possible because doctors expect the flu season to be much worse than last year, when there were very few cases. They want to avoid further strain on the health-care system already struggling with COVID-19.

For the three mRNA seasonal influenza vaccines in clinical trials now, companies need to show that combining flu strains this way doesn't lessen the effectiveness of the immune response before regulators like Health Canada consider approval.

Alyson Kelvin, a scientist at the Vaccine and Infectious Disease Organization (VIDO) at the University of Saskatchewan, has spent years studying different influenza vaccines and also works on COVID-19 vaccine candidates.

"It seems that we do have this nice, broader immunity from mRNA vaccine technology," Kelvin said. "Could you somehow target more than one influenza strain at once?"

Even if the answer is yes, Kelvin said, it's a leap to go from using one spike protein from SARS-CoV-2, the coronavirus that causes COVID-19, to also covering four circulating influenza virus strains, as the current flu shots do, with a single shot.

"It's exciting, but I think that we need to really complete the investigation," Kelvin said. The all-in-one flu and COVID-19 vaccination studies haven't reached clinical trials in humans, which normally take years to complete.

Researchers recognize that better strategies are needed to vaccinate against flu to achieve more protective responses, she said. 

Until then, public health officials hope people will continue wearing masks where necessary and washing their hands to protect against all of the pathogens that sicken people of all ages during respiratory virus season.

Written by CBC's Amina Zafar


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