A total of 300 volunteers will take part in the second-phase human trials of a SARS (severe acute respiratory syndrome) vaccine, experts said yesterday.

Scientists in Beijing will carry out trials among volunteers aged 20 to 60 to test the effectiveness of the vaccine in human beings, Zhong Nanshan, president of Chinese Medical Association, told the Guangzhou-based Nanfang Metropolis.

According to Yin Hongzhang - an official from the State Drug Administration, which is in charge of supervising trials of any new vaccine or drug - the first phase trials involved 36 volunteers at the Sino-Japanese Friendship Hospital in Beijing on May 22, 2004. By early December 2004, antibodies against the disease were found in all volunteers, without obvious side effects.

The vaccine was produced by Beijing's Sinovac Biotech Co Ltd in 2004 after SARS emerged in 2003 and again in 2004, leaving at least 350 dead, mostly in China.

Zhong did not release the exact date of the second phase or which hospitals will undertake the trials.

The 300 volunteers will undergo various medical examinations to record the persistence of antibodies over a nine-month period after the vaccine is administered, Zhong said.

The first-phase test was designed to show the vaccine could build antibodies in the volunteers without side effects, but not to see how long antibodies remain present in people's bodies, Zhong added.

Experts say only after a vaccine has passed three phases of human trials will it be licensed for use on the public.

Up to now, no volunteers who took part in the first-phase trials have reported any side effects, Zhong said.

"I am fine and have been healthy since I got the vaccine on May 22, 2004," Lan Wanli, a university student based in Beijing, said yesterday. He was the first person in the world to receive the vaccine.

Lan said he has had a medical examination to test for antibodies but the result is not yet available.

The second round of tests will involve further experimental verification in other aspects, such as dosage and the schedule for injecting the vaccine to gain a better understanding of how it can be used most effectively, experts said.

Editor: Yan