A phase I clinical trial for a recombinant novel coronavirus (2019-COV) vaccine ended recruitment for participants this week, with nearly 5,000 volunteers signing up for the trial, the Beijing News reported on Wednesday.

The newspaper cited the Chinese Clinical Trial Registry, saying volunteer recruitment ended by March 23 midnight.

A single-center, open and dose-escalation phase I clinical trial for recombinant novel coronavirus vaccine (adenoviral vector) will be tested in healthy adults aged between 18 and 60 years, according to the ChiCTR.

The trial, led by experts from the Academy of Military Medical Sciences, gained its approval on March 16 and the research is expected to last half a year.

Requiring at least 108 participants, the trial will be conducted in Wuhan, capital of Hubei, the hardest-hit region in the country.

Participants will experience 14-day quarantine restrictions after being vaccinated and their health condition will be recorded every day.

Chinese scientists have been racing to develop COVID-19 vaccines through five approaches, namely inactivated vaccines, genetic engineering subunit vaccines, adenovirus vector vaccines, nucleic acid vaccines, and vaccines using attenuated influenza virus as vectors.

So far, most teams are expected to complete preclinical research in April and some are moving forward faster, according to Wang Junzhi, an academician with the Chinese Academy of Engineering.

Wang noted that research and development of COVID-19 vaccines in China was not slower than foreign counterparts and has been carried out in a scientific, standardized and orderly way.

Xinhua contributed to this story.