Initial tests of a bird flu vaccine on monkeys in Vietnam, the country hit worst by an epidemic that has killed 47 people in Asia, have been successful, medical officials said Friday.

Vietnamese researchers injected a vaccine based on weakened H5N1 bird flu virus in three monkeys early last month and three weeks later found the monkeys were healthy and had produced antibodies.

"Researchers have repeated the injections in the monkeys and we expect results in the next two weeks," said Nguyen Tran Hien, director of the National Institute of Hygiene and Epidemiology.

Vietnam, where 14 people have died of the bird flu virus in the latest outbreak that began in December, hopes to have a vaccine ready for testing in humans later this year.

"Hopefully, in September tests will start for the vaccine on a small group of volunteers," Hoang Thuy Nguyen, head of the vaccine research group, was quoted by the state-run Tuoi Tre newspaper as saying.

Nguyen said that after the results of the repeated injection were known, researchers would need to go through several steps to ensure the safety of the vaccine before testing it on humans, most likely on the members of his group.

Asked if the next tests would include the exposure of the vaccinated monkeys to bird flu infected chickens, he said: "We are not able to conduct that type of test yet as Vietnam does not have a laboratory that is designed for such tests on animals."

Nguyen said Vietnam only has a safe laboratory designed for tests on humans and that only close co-operation with the World Health Organization would help local researchers challenge the virus by exposing the monkeys to infected poultry.

Experts said last month the effectiveness of a vaccine against a versatile and resilient virus if it mutated into a form that could easily jump between humans, their main fear, would be limited.

If it did mutate into that form, the experts fear it would trigger a pandemic which might kill millions of people in a world population with no immunity to it.

The poultry virus has killed one man and infected three - including a man and his younger sister - in northern Vietnam this month, although fewer outbreaks have been detected in poultry.

"All these infection cases have clinical factors related to slaughtering and eating poultry," Health Minister Tran Thi Trung Chien said in a report published on the ministry's website.

"There is not yet any evidence of human-to-human transmission."

The report did not mention a Cambodian woman who died in southern Vietnam in January. Some media reports have suggested she might have caught it from her younger brother, whose body was cremated before it could be tested for the virus.

Almost all the Asian victims - 34 Vietnamese, 12 Thais and the Cambodian - have caught it from infected poultry. Bird flu kills more than 70 percent of those known to have been infected, but doctors say victims can be saved if they are diagnosed early.

(China Daily March 5, 2005)