BEIJING - A COVID-19 vaccine candidate from China's Walvax Biotechnology using mRNA technology triggered a stronger antibody response against the Omicron variant of the coronavirus as a booster dose than Sinovac's shot, clinical trial data showed.

The result for Walvax's ARCoV candidate, which is yet to be peer reviewed, comes as competition for the COVID booster market intensifies in China, where more than half of the 1.4 billion population have so far received a non-mRNA booster shot.

Among 300 healthy adults vaccinated with two doses of either a Sinovac or Sinopharm vaccine around six months earlier, the neutralising antibody level against Omicron in those given an ARCoV booster was 4.4-fold higher than in those who received a Sinovac third dose, researchers said in a paper published on Tuesday.

ARCoV is the most advanced Chinese COVID-19 mRNA candidate in terms of clinical trial progress. However, a large trial started last year has yet to generate efficacy data about how well it can reduce the risk of disease or death, raising investor concerns over whether and when the shot would be eventually approved for use.

The smaller booster trial did not test ARCoV in parallel with other vaccines that have also been reported to give a stronger antibody response than a third dose of the Sinopharm or Sinovac shot.

Aside from co-developing ARCoV with Suzhou Abogen Bioscience and the Academy of Military Medical Science, Walvax is partnering with Shanghai-based startup RNACure to work on a separate mRNA COVID-19 candidate.

Sinopharm and Sinovac are also testing their Omicron specific shots as potential boosters.

(Reporting by Roxanne Liu and Ryan Woo; Editing by Kirsten Donovan)