BUDAPEST - Several countries are interested in buying an experimental bird flu vaccine which Hungary will license by March, and other states, mainly in Asia, are looking to buy the know-how, the Hungarian government said.

But things are still at a very early stage for the vaccine, which produced an immune reaction to the H5N1 strain of the virus when tested on people, spokesman Andras Batiz said.

The vaccine is being manufactured by the government and a private company called Omninvest.

"The human trials started it all off, and we are past the first step after that, which means the manufacturing of 5,000 vaccines," Batiz told a press conference.

As yet there are no firm orders and up to 25,000 vaccine shots first need to be made to test industrial production. The plant outside of Budapest would need investment to expand its capacity, Batiz said.

India, Indonesia, the Philippines and Russia are considering buying the know-how and setting up factories themselves, he said.

Human trials in Hungary have shown the jab to work against the H5N1 type of avian influenza, which has killed more than 60 people in Asia.

Bird flu remains hard for people to catch, but there are fears it could mutate into a form which can be passed from person to person, sparking a pandemic in which millions could die.

A vaccine for the current strain of H5N1 is already made experimentally by US company Chiron Corp and French company Saonfi-Aventis among others.

A vaccine would provide partial only protection against a pandemic strain of flu and would have to be reformulated to match whatever mutation eventually emerges - a process that would take months.