Scientists in the US have edged a step closer to developing a universal vaccine that would protect against multiple strains of influenza without the need for an annual seasonal flu jab.

Working in conjunction with Sanofi, a group of scientists at the National Institute of Allergy and Infectious diseases developed a vaccine concept that elicited a "more potent" immune response and broader protection than the currently licensed seasonal influenza vaccines when tested in animals.

The study was published today in the journal nature.

To make the experiment vaccine, the protein ferritin was fused with hemagglutinin, a protein found on the surface of the influenza virus, which hardly vary between strains.

In a study on mice, a single dose of the vaccine triggered an immune response comparable to two doses of the currently licensed seasonal flu jab.

The scientists also tested the vaccine’s ability to protect ferrets from infection with a 2007 strain of H1N1 influenza virus.

One day after exposure to the virus, the vaccinated ferrets had significantly lower influenza virus levels than those that were not immunised.

Although further testing is needed, the HA-ferritin nanoparticle approach shows promise for development of more broadly protective vaccines for influenza, the authors noted.

Image: The spikes on the surface of the influenza virus hardly vary between strains. Credit: