International Vaccine Institute researcher Song Joo Hye and her colleagues found that the sublingual (under the tongue) administration of an experimental flu vaccine was highly effective in protecting mice, the institute said in a statement.

'When the flu vaccine was applied under the tongue, animals developed robust immune responses in their lungs and were fully protected from the disease when later exposed to a severe form of influenza virus,' it said.

As an alternative to needle jabs, flu vaccines can currently be sprayed into the nose. But with this method there is a theoretical possibility of directing viruses to the central nervous system.

'The new studies suggested that this under-the-tongue method of vaccine administration poses no risk of antigen redirection to the central nervous system,' said Kweon Mi Na of the IVI, who oversaw the study.

Cecil Czerkinsky, IVI deputy director-general for laboratory science, said in the statement that the studies 'provide a basis for further human testing of this alternative form of needle-free vaccination.' 'Aside from its convenience, sublingual vaccination appears to disseminate immunity to a broader range of organs than the classical routes of injecting or ingesting vaccines,' he said.

If the findings were replicated in humans, they could pave the way for the development of a new generation of vaccines against respiratory infections including bird flu viruses, he said.

John Clemens, IVI director-general, called the studies an important milestone.

'Sublingual vaccination is an entirely new approach to the delivery of vaccines; this approach offers the possibility of vaccinating against a variety of infections without the risks posed by delivering vaccines with needles,' he said. -- AFP