China published the initial results of the world's first clinical testing of a SARS vaccine on Wednesday, saying the four human guinea pigs were doing fine.
Seventy-two hours after receiving their injections, the four - three men and one woman - had shown no adverse reactions, the Xinhua news agency reported.
However, there is more than six months to go before the experiment is completely over.
It could take even longer - probably years - before a SARS vaccine is properly developed and enters into mass production.
The four are the first out of 36 volunteers who have agreed to participate in the test, jointly developed by China's Science and Technology Ministry and the Beijing Kexing Vaccine Company.
Severe Acute Respiratory Syndrome originally emerged in south China at the end of 2002, and eventually struck 32 countries, infecting some 8,000 people and killing nearly 800 before subsiding.
China was worst hit, accounting for 349 deaths and 5,327
infections.
