BEIJING • One of China's front-running coronavirus vaccine candidates was shown to be safe and triggered immune responses in a combined early-and mid-stage test in humans, researchers said.

The potential vaccine, dubbed BBIBP-CorV, is being developed by the Beijing Institute of Biological Products, a subsidiary of the China National Biotec Group (CNBG).

It has already been approved for an emergency inoculation programme in China targeting essential workers and other limited groups of people facing high infection risk.

However, whether the shot can safely protect people from the disease will become clear only when final Phase 3 trials - which are ongoing outside China - are complete.

Separately, a US$60 (S$81.50) double-dose experimental coronavirus vaccine is being made available to some residents in an eastern Chinese city, health officials have said - the first details of a mass rollout for an as-yet unproven vaccine.

Officials in Jiaxing city said on Thursday that residents aged between 18 and 59 with "urgent needs" can seek consultations at clinics for a Sinovac Biotech vaccine that the authorities have been giving to groups such as medical workers.

The authorities did not say how many in the city had been given the vaccine, which comes in two doses, administered up to 28 days apart and costing 400 yuan (S$81.50).

BBIBP-CorV is one of at least 10 coronavirus vaccine projects globally to have entered Phase 3 trials, four of which are led by Chinese scientists, according to the World Health Organisation.

It did not cause any severe side effects, while common mild or moderate adverse reactions included fever and pain in injection sites, according to a paper published on Thursday in medical journal The Lancet.

The results came from a combined Phase 1 and Phase 2 trial involving more than 600 healthy adults conducted between April 29 and July 30.

Two injections of BBIBP-CorV at three different doses generated antibodies in all recipients of each group, including older participants, although the data does not prove the vaccine is efficacious, researchers at the CNBG subsidiary, Chinese disease control authorities and other research institutes said in the paper.

REUTERS, AGENCE FRANCE-PRESSE