BEIJING, May 8 (Xinhua) -- A joint Chinese research team has recently published the results of the first animal experiment of one COVID-19 vaccine candidate in the journal Science.

A purified inactivated COVID-19 vaccine candidate (PiCoVacc) confers complete protection in non-human primates against COVID-19 strains circulating worldwide by eliciting potent humoral responses devoid of immunopathology, according to the research result.

In this animal experiment, Chinese researchers used the vaccine candidate PiCoVacc, which was jointly developed by Beijing Sinovac Biotech Ltd. and multiple Chinese research institutions.

PiCoVacc was approved for the first and second phases of clinical trials by the National Medical Products Administration on April 13. It was also among the first batch of vaccine candidates approved for clinical research in China.

The experimental results showed that PiCoVacc induced specific neutralizing antibodies of the novel coronavirus in mice, rats and non-human primates. These antibodies neutralized multiple novel coronavirus strains, which were representative strains worldwide.

Researchers evaluated the immunogenicity and protective efficacy of PiCoVacc in rhesus macaques, a non-human primate species that has been found to be infected with a COVID-19-like disease.

The results show that all vaccinated macaques were largely protected against novel coronavirus infection with very small histopathological changes in their lungs. Viral loads also decreased significantly in all vaccinated macaques, but increased slightly in control animals.

Through clinical index and biochemical indicators, researchers found no fever and weight loss in any of the vaccinated macaques, which maintained normal appetite and mental state. There were likewise no significant changes in the lymphocyte subpopulation ratio and key cell factors between vaccinated macaques and the control group.

PiCoVacc did not lead to significant pathological features according to the pathological evaluation of multiple organ tissues.

This indicates the PiCoVacc candidate vaccine was safe for rhesus macaques, the researchers said.

China has approved three COVID-19 virus vaccine candidates for clinical trials. Chinese researchers are also racing against time in developing multiple other vaccines through various technological approaches.

Officials from the Ministry of Science and Technology noted that despite the exceptional circumstances, the vaccines developed must be based on scientific, safe and effective rules.