mRNA technology for universal flu vaccine shows early promise in US study

A new mRNA vaccine targeting all 20 known strains of influenza has shown early promise in a new study by researchers at the University of Pennsylvania's Perelman School of Medicine, potentially paving the way to a universal flu vaccine that might help prevent future pandemics.

The World Health Organization cites vaccination as the current principal means of reducing or counteracting influenza mortality and morbidity burden, but the constantly evolving nature of influenza viruses requires continuous global monitoring and frequent reformulation of influenza vaccines.

Each year, even when currently available vaccine strains match circulating influenza virus strains well, those vaccines typically offer only around 40% to 60% protection, with even lower protection in years with poor matching of strains.

A universal flu vaccine would eliminate the guesswork that goes into identifying and developing viral composition of influenza vaccines each year, allowing the immune system to recognise any flu virus it might encounter in the future.

“The idea here is to have a vaccine that will give people a baseline level of immune memory to diverse flu strains, so that there will be far less disease and death when the next flu pandemic occurs,” said study leader Scott Hensley, professor of microbiology at the Perelman School of Medicine at the University of Pennsylvania.

The experimental vaccine, which includes 20 different types of haemagglutinin antigens of type A and B influenza viruses, elicited high levels of cross-reactive and subtype-specific antibodies in mice and ferrets that reacted to all 20 encoded antigens.

Antibody levels induced by the vaccine remained unchanged for at least four months, according to the report published in the journal Science, and reduced signs of illness when exposed to a different type of flu not in the vaccine.

The two-dose vaccine uses the same mRNA technology used in successful COVID-19 vaccines, delivering tiny lipid particles containing mRNA instructions for cells to create replicas of haemagglutinin proteins that appear on influenza virus surfaces.

The universal flu vaccine would not necessarily prevent infection, Hensley explained, but would aim to stimulate a memory immune response that could be quickly adapted to new pandemic viral strains.

“It would be comparable to first-generation SARS-CoV-2 mRNA vaccines, which were targeted to the original Wuhan strain of the coronavirus,” said Hensley. “Against later variants such as Omicron, these original vaccines did not fully block viral infections, but they continue to provide durable protection against severe disease and death.”