China's Walvax says has most participants for large mRNA COVID vaccine trial

BEIJING (Reuters) -China's Walvax Biotechnology has recruited most of the 28,000 participants needed for a large clinical trial of its mRNA COVID-19 vaccine candidate, a senior company official said on Thursday.

China has yet to approve a Chinese vaccine of the novel messenger RNA (mRNA) technology and has yet to import a foreign mRNA vaccine.

The issue has become more urgent as studies have shown China's most frequently used shots from Sinovac and Sinopharm are less effective against the highly contagious Omicron than against some previous variants.

From next week, a Phase III trial for Walvax's potential mRNA vaccine will shift its focus from recruiting participants to identifying potential COVID-19 infections for data analysis, Walvax vice chairman Huang Zhen said on Thursday.

He declined to provide any timeline for the trial.

"The first step is to identify all those cases and not to miss any," Huang said in a phone call, citing concerns that some participants might not report their disease for fear of being quarantined.

Recruiting participants from overseas for the trial was slow initially, but accelerated after researchers moved the recruitment to smaller, less-vaccinated cities, Huang said.

The ARCoV vaccine, which Walvax co-developed with Suzhou Abogen Biosciences and a Chinese military-backed research institution, is being tested in a Phase III trial across countries including China, Mexico and Indonesia.

Ying Bo, founder of Abogen, said in an investor conference call late on Thursday that the rate of fever after taking the vaccine declined significantly in the Phase III trial compared with in earlier smaller trials, responding to concerns over the adverse reaction from the vaccine.

Peer-reviewed result from a Phase I trial showed that 30% of participants who took the vaccine at the same dosage as the one moved in Phase III tiral had severe fever.

Finding and analysing cases from a Phase III trial is essential to calculating a vaccine's efficacy, which usually requires comparing the number of cases among those vaccinated and those not.

Another China-based clinical trial to test ARCoV as a booster dose has recruited more than 1,000 participants and collected blood samples for analysis, Huang said, without saying when the results could be ready.

Walvax's facilities have an annual capacity to make a total of 400 million doses of the vaccine in the form of bulk substance, and the company intends to increase that capacity, Huang said.

(Reporting by Roxanne Liu and Ryan Woo; editing by Barbara Lewis)