By Natalie Grover and Josephine Mason
HONG KONG, Jan 5 (Reuters) - China's CanSino Biologics Inc 6185.HK688185.SS reported on Thursday "positive" interim data on its experimental COVID-19 mRNA booster vaccine in a mid-stage clinical trial.
This is the first early data on one of China's first home-grown potential vaccines based on mRNA technology as the country races to tame a severe outbreak of infections after abandoning its strict "zero COVID" policy last month.
The 433-person trial of those aged 18 and above tested a booster shot of the vaccine, called CS-2034, in people who had already received three doses of an inactivated vaccine, the drugmaker said in a filing to the Hong Kong stock exchange.
The new vaccine was tested against an additional shot of the inactivated vaccine, it said.
Inactivated vaccines, now used in China, contain a dead form of the pathogen, in this case the COVID-causing virus SARS-COV-2, to help the immune system trigger a response without causing illness.
China has nine domestically-developed COVID vaccines approved for use, including inactivated vaccines, but none have been adapted to target the highly-transmissible Omicron variant and its offshoots that are currently in circulation.
In the CanSino trial, 28 days following the booster shots, adults in the CS-2034 group had virus-neutralizing antibodies at levels that were 27 times as high as those in the inactivated vaccine group against the original Wuhan strain, and 23 times higher against the BA.1 Omicron variant, the company said.
According to data reported by the World Health Organization on Wednesday, China's CDC analysis showed a predominance of Omicron sublineages BA.5.2 and BF.7 among locally acquired infections.
Spiraling infections are a particular concern in the world's most populous nation because the number of people who have had a booster shot is quite low, especially for the elderly.
The overall vaccination rate in the country is above 90%, but the rate for adults who have had booster shots drops to 57.9%, and to 42.3% for people aged 80 and older, according to Chinese government data released last month.
Overseas-developed vaccines are unavailable to the general public in mainland China, which has relied on inactivated shots by Sinopharm and Sinovac and other domestically developed options for its vaccine rollout.
While the shots are safe, some studies have suggested they are not as effective as other vaccines, such as the mRNA shots developed by Pfizer-BioNTech and Moderna.
(Reporting by Meg Shen and Natalie Grover; Editing by Josephine Mason and Tomasz Janowski)
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