BEIJING -- A China-developed recombinant protein subunit vaccine against COVID-19, which has been approved for emergency use, has shown to be safe and can elicit an antibody response in early-stage trials, according to a study published this week in The Lancet Infectious Diseases journal.

The results of phase-1 and phase-2 trials show that 97 percent of participants who received three 25-microgram doses of the vaccine produced antibodies effective in neutralizing the virus, and their antibody levels were higher than that of recovered patients, indicating stronger immune responses induced by the vaccine, the study said.

China on March 10 approved the emergency use of the vaccine, which was jointly developed by the Institute of Microbiology under the Chinese Academy of Sciences and Anhui Zhifei Longcom Biopharmaceutical Co. Ltd.

According to researchers, the early-stage trials, which were randomized, double-blind and placebo-controlled, involved 950 healthy participants aged between 18 and 59. No serious adverse events have been found.

After two doses of the vaccine, 76 percent of the participants produced neutralizing antibodies. After three doses of the vaccine, 97 percent produced neutralizing antibodies, said the study.

Researchers are conducting phase-3 trials in Uzbekistan, Indonesia, Pakistan and Ecuador. Uzbekistan approved the use of the vaccine on March 1.

China has approved four vaccines against COVID-19 for conditional marketing and another vaccine for emergency use.