The trial, to be carried out with US government assistance, will be the latest of several global efforts to develop a vaccine for mass production, with research also going on in the United States, Europe and elsewhere in Asia.

The news comes as a new wave of bird flu sweeping Vietnam has killed a 20-year-old man.

The outbreak infected four other people and triggered more than 100 outbreaks in poultry since last month.

"Preparations for the clinical test of a human vaccine have been basically completed," said Nguyen Tran Hien, director of the National Institute of Hygiene and Epidemiology in Hanoi. He expects testing to start as early as July, with the trial to wrap up next year.

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Volunteers will not be exposed to H5N1 - the strain that has killed 191 people worldwide since 2003 - but will be given the vaccine so experts can look for early evidence of safety and to test their antibody response.

American experts are providing technical assistance, and Washington has granted US$1 million (HK$7.8 million) to Vabiotech, a company spun off from the institute.

The Vietnam trial is one of several efforts worldwide to find a vaccine that could be mass produced in case of a pandemic.

US firm Baxter Healthcare will in July start clinical trials of a bird flu vaccine in Hong Kong and Singapore, using a virus strain from Indonesia.

The NIHE project is one of Vietnam's three research drives for a vaccine, along with work at the Pasteur Institute in Ho Chi Minh City and vaccine producer IVAC in Nha Trang. In April, the World Health Organisation said Vietnam, Indonesia, Thailand, Brazil, India and Mexico will receive grants to produce flu vaccine locally and bolster global protection.

On another front, Swiss drug giant Roche's Japanese partner says there will be more research on Tamiflu to probe assertions the drug has caused young people to harm themselves.

Tamiflu is prescribed for the common flu and has been stockpiled in some countries as a frontline drug in the event of a bird flu pandemic.

But Japanese authorities say more than 100 people - mostly young children and teenagers - have behaved abnormally after taking Tamiflu. Eight died by jumping from buildings, running into traffic or other rash actions.

Earlier probes in Japan, the largest importer of Tamiflu, and the US have not found a link to erratic behavior. But Japanese authorities told doctors not to give Tamiflu to young people.

Chugai Pharmaceutical, which imports Tamiflu, will join Roche in conducting new tests that involve volunteers. But Roche has denied there are dangerous side effects of its drug.

AGENCE FRANCE-PRESSE