Moderna is banking on a combined COVID, flu and RSV vaccine. Will it work?

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Moderna is actively promoting a combined COVID-19, flu and RSV vaccine, something that aims to target three of the most serious respiratory illnesses circulating each year in a single shot.

But while a safe and effective vaccine would be welcome as Canada faces a surge in pediatric RSV cases, stubbornly high COVID hospitalizations and deaths and steeply rising flu cases, the pharmaceutical company hasn't released data to support the vaccine's safety or efficacy.

Moderna president Stephen Hoge told CBC News he hoped the three-in-one vaccine would be submitted to Health Canada for regulatory approval within a year.

"We really do think that the triple combo — the flu, plus COVID, plus RSV — is really going to be the ideal shot for us to get every year," he said in an interview this week.

"And honestly it just takes one shot to try and prevent all of that, and so we'll try and add as much bang for the buck into that shot as we can and hopefully help protect people through winter seasons in the years to come."

But without solid data from clinical trials this combined vaccine may never come to fruition.

Moderna's decision to promote its vaccine before completing Phase 3 clinical trials — in which the vaccine would be tested on a larger group as part of a randomized, double-blind study — is controversial. It's also raised concerns from vaccine researchers and infectious diseases experts about the motivations behind prematurely marketing the shot.

"There's still more questions than answers, obviously, with releases like this that come from companies without accompanying data," said Matthew Miller, a vaccine researcher and associate professor of infectious diseases and immunology at McMaster University. 

"I think we need to be really cautious. We have no data on safety, no data on effectiveness or efficacy or age groups. How would you handle updating various components of that vaccine? Lots and lots of questions."

Alyson Kelvin, a virologist at the Vaccine and Infectious Disease Organization at the University of Saskatchewan, said that while the flexibility of mRNA technology for future vaccines is "exciting," it's essential to see safety and efficacy data from clinical trials.

"What is it claiming to do? Is it claiming to reduce disease, or block infection or reduce hospitalization? And is it effective in what it's saying it's supposed to do?" she said. "It's always best to have the data to back up your claims."

Dr. Isaac Bogoch, an infectious diseases physician at Toronto General Hospital and member of Ontario's COVID-19 vaccine task force, said it's not yet known what level of protection an RSV vaccine would provide or how frequently shots would be needed.

"I would be very careful now to assume that making a three-in-one vaccine that's administered annually is needed," he said. "Clearly, we need vaccines for all three, but we don't know what the frequency of vaccination is going to be."