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A Chinese mRNA vaccine candidate showed a sharp drop in neutralising antibody activity against Omicron in a small study, but a booster readily induced antibody production in animal tests, researchers said.
The ARCoV vaccine, jointly developed by the Academy of Military Medical Sciences (AMMS), Suzhou Abogen Biosciences and Walvax Biotechnology, is being tested in an international Phase III clinical trial.
It is China’s locally developed mRNA (messenger RNA) vaccine candidate furthest along in trial progress.
The country has yet to approve mRNA vaccines developed locally or overseas, but has vaccinated 87.1% of its population using several domestically developed shots based on other technologies.
In a lab study analysing samples from 11 vaccinated people, eight demonstrated “low but detectable” neutralisation activity against Omicron, researchers said in a letter to editors published in the journal Cell Research.
The neutralising antibody level against Omicron showed a 47-fold reduction compared with the level against a “wild-type”that contains no major mutations, said the paper published on Monday.
But in animal tests, a third dose, given about nine months after the second shot, readily induced the production of neutralizing antibodies against Omicron and a wild-type strain, it said.
“Our data presented here clearly demonstrate that a third dose of ARCoV would probably lead to a sharp increase in neutralisation antibodies not only against the WT (wild type) SARS-CoV-2 but also the newly Omicron variant,” the study said.
China, which is battling small but constant outbreaks of COVID-19 infections, has boosted around one third of its 1.4 billion people, using non-mRNA shots.
The researchers said they also conducted animal tests on two new mRNA vaccine candidates targeting Omicron and the result showed that the induced antibody levels were comparable to those elicited by the original ARCoV.
Authors of the paper include scientists from AMMS and Suzhou Abogen Biosciences, as well as researchers with other Chinese institutes.
A Walvax executive said last month it had recruited most of the 28 000 participants it planned for the Phase III trial and was now looking to focus more on identifying COVID-19 infections among trial participants for data analysis.