BEIJING: Chinese researchers are testing mixing two COVID-19 vaccines developed by CanSino Biologics and a unit of Chongqing Zhifei Biological Products respectively, according to clinical trial registration data.

Earlier this month, the director of the Chinese Center for Disease Control and Prevention said the country was "formally considering" giving people COVID-19 vaccines developed with different technologies as a way of further boosting vaccine efficacy.

A trial expected to involve 120 participants will test the safety and ability to trigger immune response of a dose of CanSinoBIO's Ad5-nCoV treatment, followed by a dose of ZF2001 from Anhui Zhifei Longcom Biopharmaceutical, at 28-day or 56-day interval, according to clinical trial record site ClinicalTrials.gov maintained by a department under the National Institute of Health of the United States.

The trial, under way in the eastern Chinese city of Nanjing, is sponsored by disease control authorities in Jiangsu province, according to the record.

Both vaccines are included in China's mass vaccination drive.

CanSinoBIO said interim data from overseas Phase III clinical trials showed its Ad5-nCoV vaccine was 68.83% effective at preventing symptomatic COVID-19 disease two weeks after one injection, while the rate fell to 65.28% four weeks after one shot.

Chinese researchers also running trials for two-dose-based vaccination of Ad5-nCoV, as well as an inhalation version of the vaccine.

No efficacy readings has been made available from Phase III trials for Zhifei Longcom's ZF2001 vaccine, which requires three injections when used on its own.

CanSinoBIO and Chongqing Zhifei Biological Products were not immediately available for comment.