Flu vaccines may someday be slipped under the tongue rather than jabbed in the arm, Korean researchers say.

A team of researchers from the International Vaccine Institute in Seoul suggest vaccines placed under the tongue "could be more effective than traditional approaches for vaccinating against both seasonal and pandemic flu."

Testing the vaccine in mice, the researchers found that two doses of their under-the-tongue vaccine provided protection against what would otherwise be deadly doses of both live and inactivated flu viruses.

Giving the vaccine orally enhances protection against the virus by provoking an immune responses in the mucus membranes, they said, which can guard against pathogens at their entry point, as well as by boosting responses in the immune system. 

Additionally, they said, an oral vaccine prevents viruses from travelling into the central nervous system, a rare but potentially harmful complication from vaccination injections.

The under-the-tongue vaccination may give immunity to a broader range of organs than other means of vaccination, such as injection or ingestion, Dr. Cecil Czerkinsky, deputy director-general for laboratory science at the Institute, said in a statement.

"These studies provide a basis for further human testing of this alternative form of needle-free vaccination."

With further testing, the researchers said vaccines administered under the tongue could "pave the way for the development of a new generation of vaccines that could be used for mass vaccination against respiratory infections, including the pandemic avian-human influenza viruses."

The doses could even be flavoured, they said.

Their findings are published in the journal Proceedings of the National Academy of Sciences.

With files from the Associated Press