BEIJING (REUTERS) - A potential Covid-19 vaccine being developed by Chinese researchers showed promise in trials in monkeys, triggering antibodies and raising no safety issues, researchers said, and a human trial with more than 1,000 participants is under way.

The vaccine candidate, called BBIBP-CorV, induced high-level neutralising antibodies that can block the virus from infecting cells in monkeys, rats, guinea pigs and rabbits, researchers said in a paper published online by medical journal Cell last Saturday (June 6).

"These results support the further evaluation of BBIBP-CorV in a clinical trial," researchers said in the paper.

BBIBP-CorV - developed by the Beijing Institute of Biological Products, which is affiliated to state-owned China National Pharmaceutical Group (Sinopharm) - is among five candidates China is testing in humans.

More than 100 potential Covid-19 vaccines are in various stages of development around the world.

Among front runners currently in human trials are those being developed by AstraZeneca, Pfizer, BioNtech, Johnson & Johnson, Merck, Moderna, Sanofi, and China's CanSino Biologics.

As well as appearing safe and able to generate an immune response in animals, BBIBP-CorV did not appear to trigger antibodies that could boost the infection - a phenomenon known as antibody-dependent enhancement (ADE) - the researchers said, although this does not necessarily guarantee that ADE will not occur in human tests.

Apart from BBIBP-CorV, Sinopharm, which has invested 1 billion yuan (S$196 million) in vaccine projects, is testing in humans another vaccine candidate developed by its Wuhan-based unit. The two shots have been given to more than 2,000 people in clinical trials.