Doctors have already warned a pandemic of bird flu is inevitable and could kill up to 50,000 people in Scotland.

In March, ministers announced plans to cope with such an outbreak, including setting aside GBP 14.6 million worth of anti-viral drugs to treat the flu. Now Indonesia has reported its first human death linked to bird flu -- known as the H5N1 virus -- taking the death toll in southeast Asia to 57.

Mortality Could Be 30 Percent

At the moment, bird flu appears to pose a limited threat to humans because it cannot be spread easily from person to person.

But the outbreak in Asia has led to concern among scientists.

Peter Openshaw, the head of the respiratory infections section at the national heart and lung institute, Imperial College, London, said: "It's difficult to know if a major outbreak is about to happen, but mutated H5N1 bird flu that spreads between people would be much harder to control than SARS or smallpox.

"The human mortality with H5N1 bird flu could be 30 percent and an epidemic could infect 50 percent of the world's population. I am much more concerned about this than terrorist threats."

Patricia Hewitt, the health secretary, announced yesterday that manufacturers are to be invited to tender for a contract to supply the H5N1 vaccine.

She said: "I have decided it would be prudent to purchase a limited quantity of H5N1 vaccine which could be used to help protect those that need it most, such as NHS workers. We will also be able to carry out further research so that we can find out how the vaccine can be used most effectively."

Vaccine May Not Be Effective

Because the vaccine plans are for a national emergency, rather than for regular health care, they cover the whole of the UK.

However, the health service in Scotland will have separate plans to allow for differences in policy, and health agencies across the UK will be involved in monitoring any outbreak.

Jim McMenamin, a consultant epidemiologist with Health Protection Scotland (HPS), said bird flu was a risk to Scotland and it was the responsibility of health workers across Britain to be prepared.

"They have been looking at this for some time on the available evidence that there continues to be a threat of avian influenza in southeast Asia. In response to that threat, this is a welcome development."

If a pandemic does occur, a vaccine could be used in a number of ways.

If the flu affects a particular sector of the population, such as young children or the elderly, it could be given to them. Or, if a certain part of the country is affected, it could be given to the surrounding population. Most commonly, it could be given to key workers, particularly those in hospitals, to ensure that public services are maintained.

However, given the virus constantly changes, the vaccine will not necessarily be effective against the threat.

HPS, along with the Health Protection Agency in England, will assist in any research to find out how the vaccine works and how effective it can be.