Question marks have arisen over Hungary's bird flu vaccine since the government late last year announced that it would be the first to develop a vaccine against the deadly virus.

Many health experts, including the European Commission's director of public health, Fernand Sauer, pointed out that the vaccine was only useful as a "trial run" and would have no practical use in the event of a real pandemic.

Klaus Stohr, the World Health Organization's advisor on influenza pandemic vaccines, said last Friday: "Hungary's results initially showed that the vaccine would contain 30mg of antigen, but it turned out that there may have only been 6mg, which would have made it ineffective."

Stohr also revealed that Hungary had failed to respond to calls for independent verification.

The vaccine against the deadly H5N1 strain of the bird flu, produced by Omninvest and backed by the government, received the green light for domestic production in March.

Since then, however, the firm has refused to release any details for independent reviews and has not submitted it to the London-based European Medicines Agency (EMEA) for licensing.

So far, no countries have actually purchased Omnivest's vaccine or technology, but Omninvest CEO Ferenc Zimonyi said negotiations were underway.

Zimonyi also defended both the efficiency of the vaccine and the decision not to submit it to the EMEA or the WHO.

"For the time being we have considered it untimely to submit the vaccine and its documentation to EMEA," he said. "We are not averse to the submission at an appropriate time, but we have to take into consideration that our clinical trials are not yet finished."

And Mihaly Kokeny, the Hungarian government commissioner, calls the Hungarian bird flu vaccine "the best."

Even the human tests carried out so far demonstrated that the vaccine contained a sufficient amount of antigen, Kokeny said last weekend.