One shot targets 20 flu subtypes

A universal flu vaccine that would protect people against new or unfamiliar flu strains has long been a goal of researchers and pharma companies. Results from a new study suggest that the messenger RNA (mRNA) vaccine platform used to make some widely used COVID-19 vaccines might be the way (Science 2022, DOI: 10.1126/science.abm0271).

Vaccines for seasonal flu typically target antigens for just one or two circulating influenza virus strains. A universal flu vaccine would give much broader protection by inducing the body to create long-lasting antibodies against all flu strains currently circulating the world. Researchers have previously attempted to do that by designing a handful of antigens that could induce the body to make antibodies that can each bind to multiple forms of the hemagglutinin (HA) protein that dots the outside of flu virus particles. In contrast, the team led by Scott E. Hensley of the University of Pennsylvania make their vaccine candidate with sequences of mRNA that code for 20 different HA proteins. Their method ensured that the vaccine had a representative HA from every known influenza subtype.

The researchers then injected a cocktail of lipid nanoparticles encapsulating the different mRNAs into mice and ferrets. The vaccine caused the animals to create antibodies against all 20 subtypes and protected the animals from the flu.How long that protection lasts is unclear. Still, the experiments show how flexible the mRNA platform can be for vaccine design, Alyson A. Kelvin and Darryl Falzarano of the University of Saskatchewan write in a perspective accompanying the paper (Science 2022, DOI: 10.1126/science.adf0900).