New mRNA vaccine targeting all known flu strains shows early promise

A new mRNA vaccine targeting all known flu strains in a single shot is showing early promise in animal studies and is opening the door to a wide range of possibilities with the vaccine technology — including potentially preventing the next influenza pandemic. 

University of Pennsylvania researchers published their findings in the journal Science Thursday, showing the vaccine produced high levels of antibody protection in mice and ferrets against all flu strains, which could one day help pave the way for a universal flu shot.

The research rapidly lifts mRNA technology to new heights and builds off the progress made in the COVID-19 pandemic in accelerating the development of the new vaccine platform, which has already been effectively used in billions of people worldwide. 

"Our approach was to make a vaccine that encoded every influenza subtype and lineage that we know about," said Scott Hensley, an immunologist at the University of Pennsylvania in Philadelphia and one of the lead authors of the study.

"The goal was to establish a baseline level of immune memory that could then be recalled when a new pandemic strain emerges."

Unlike seasonal flu shots that protect against existing circulating strains each year but offer little protection against strains that can spill over from animals and spark pandemics, like H1N1 in 2009, this shot could theoretically provide immunity against all new flu strains. 

"We're still in preclinical testing at this phase, we are planning a Phase 1 human study, but so far from animal models it does look like this vaccine achieved our goal of inducing immune memory in a broad way," Hensley said. 

"Imagine if the population was primed with this vaccine, what we might see is not necessarily protection from infection with new pandemic strains but a reduction in hospitalizations and severe disease — and that's really our main goal."

While a potential vaccine could be years away since it still needs to successfully undergo human trials, developing a flu shot that can target all 20 known influenza A and B strains is an astonishing scientific feat.

"It really shows that we can use mRNA vaccines in ways that we really hadn't thought of before," said Alyson Kelvin, a virologist at the University of Saskatchewan's Vaccine and Infectious Disease Organization who co-wrote an independent perspective on the study in Science.

"This is just the beginning of where we can take mRNA-based vaccines." 

The research opens up a world of new possibilities with mRNA vaccine technology.

And it also brings hope of one day preventing hundreds of thousands of hospitalizations and deaths from the flu globally each year — if it passes clinical trials and regulatory approval.

"This is a way to cover a huge family of viruses that causes a large burden of disease each year around the world," Kelvin said. "As well, there's continual threats of a new influenza virus spilling over. So it could not only cover what we're currently dealing with, but what we don't know."