Plans for the second phase of clinical trials of a SARS (severe acute respiratory syndrome) vaccine were released on Monday.

Yin Weidong, in charge of China's SARS vaccine research program, said 300 volunteers are expected to be involved.

According to Yin, the WHO received China's complete research procedure report on the inactivated SARS vaccine on June 1 and has since made recommendations for the second phase of trials.

WHO suggested that a gender balanced group of 300 volunteers aged between 20 and 60 be chosen for two clinical trial bases. In the first three months, volunteers would be injected three times and then observed over the following nine months. Each trial would involve 100 people injected with inactivated SARS vaccine and 50 with placebo.

Academician Zhong Nanshan, a well-known figure in the fight against the SARS epidemic in 2003, said the number of trial bases should be increased and the number of people in each base reduced. In order to ensure safety and better select among immune procedures, he said three bases would allow for more variation in dosage and timing of injections.

Yin said the first phase of clinical trials, completed last December, was primarily to establish the safety of the inactivated vaccine -- the second will aim to confirm the best way to administer the vaccine while still monitoring safety.

Whether to proceed with the second phase has been the subject of debate among specialists; some have questioned whether so many resources should be spent on trials, describing the likelihood of another outbreak as unlikely, while others have said the risk of leakage from laboratories was too great.

The government is currently evaluating the first phase in order to decide whether to approve the second, but Zhong expressed strong support for it.

"The country should invest more in preventing and finding contagious sources and developing a vaccine," he said, despite the chance of the recurrence of SARS being very slim.

An inactivated vaccine was produced last May following a year of intense research. Trials among 36 volunteers proved effective and safe in the first phase of human tests that began on May 22 last year, according to Beijing-based Sinovac Biotech Co Ltd, which produced the vaccine. Antibodies, without obvious side effects, were found in all volunteers who had received the test vaccine.

The vaccine will only be able to be sold to the public once it has passed a third round of human trials.

(China.org.cn by Wang Qian, June 30, 2005)