Scientists unveiled a concept vaccine against flu Wednesday they said may protect against various strains with a single jab.

Tested in ferrets, considered good human models, the synthetic vaccine uses nanotechnology to attack parts of the influenza virus that different strains have in common, they wrote in the journal Nature.

"It provides a basis for development of universal influenza vaccines and for more rapid generation of vaccines during new outbreaks," study-co-author Gary Nabel of the National Institute of Allergy and Infectious Diseases (NIAID) in Maryland told AFP.

Human trials have yet to be done, but the team was encouraged by the extra safety of the vaccine, which doesn't need to be manufactured from viruses in chicken eggs in the lab, as is the case for seasonal vaccines against flu strains often carried by birds.

It is also much faster to make.

The new design incorporates the protein ferritin, fused genetically with hemagglutinin (HA) -- a protein found on the surface of the influenza virus.

The fusion results in a microscopic nanoparticle with eight protruding spikes that forms the basis for the vaccine antigen, which is what spurs the immune response.

Lab animals given the vaccine were protected not only against the strain of H1N1 influenza from which the HA was derived, but a broader range of strains of the constantly mutating influenza virus.

"The novel vaccine concept works by stimulating antibodies that hitch themselves to the parts of the influenza virus that stay consistent across different strains," said a NIAID statement.

The immune response was also stronger than with existing vaccines.

NIAID called the concept "an important step forward in the quest to develop a universal influenza vaccine -- one that would protect against most or all influenza strains without the need for an annual vaccination."

Commenting on the study, Imperial College London virology lecturer Mike Skinner said the development was "really promising", though the concept drug would need several years to pass clinical trials and regulatory hurdles.

"Although it might be more broadly effective than the current vaccines, it is too early to tell how easily or how frequently resistant viruses would arise in the future, given that candidate pandemic viruses are continually being produced in wild birds," Skinner said.