Chinese scientists said Sunday four volunteers are in good conditions in the first day of the world's first clinical testing of a vaccine for severe acute respiratory syndrome (SARS).

The volunteers, including three healthy male students and a female from Beijing-based universities, were injected a SARS vaccine or a SARS-virus free placebo Saturday afternoon, sources in charge of the experiment said.

During two hours of observation period after the inoculation, no abnormal reaction was observed and they left China-Japan Friendship Hospital where the testing was conducted.

The volunteers would take blood tests and be observed for reaction everyday in the first three days, and the whole observation process would last 210 days.

Neither the volunteers nor the doctors were informed of whether the injection is a vaccine or a SARS-virus free placebo, the sources said.

The four are the first group of 36 healthy volunteers aged from21 to 40 who are selected for the testing. They will be inoculated either with the vaccine or a placebo.

Doctors of the hospital said they are well prepared to deal with any emergencies that might happen to the volunteers.

Approving the first phase of the clinical testing in January this year, China has become the first nation in the world to approve clinical testing of the vaccine on humans.

The vaccine was developed by Beijing Kexing Bio-product Co., Ltd.