Researchers have constructed an investigational universal flu vaccine out of nanoparticles. 

The vaccine, which has been successfully tested on mice, is designed to protect against a broad range of variants of the disease, by training the immune system to spot core and unchanging features of the virus.

It will still have to overcome many hurdles before it could be approved for use on humans but researchers said that it was at the very least proof of the principle of a new way of engineering vaccines.