BEIJING - A China-developed mRNA COVID-19 vaccine as a third booster dose has been shown in human trials to be safe and able to induce an immune response against the Omicron variant.

AWcorna, previously known as ARCoV, which encodes the receptor-binding domain of SARS-CoV-2 spike protein, is now being tested in the final stage of multiple-center phase-3 trials.

In a randomized clinical trial, scientists from the Academy of Military Medical Sciences in China, Guangzhou Institute of Respiratory Health, and Walvax Biotechnology Co Ltd enrolled 300 adults who have received a two-dose inactivated vaccination.

All participants were randomly assigned to either the AWcorna or inactivated vaccine booster group, and the neutralization and antibody titers in their bodies were assessed at pre-booster, 14- and 28-day post-booster, according to an article published online this week in the journal Cell Research.

AWcorna booster induced a 66-fold increase against wild-type SARS-CoV-2, and the neutralization antibody titers are over three times more than those in the inactivated vaccine group, according to the researchers.

Although the neutralization antibody titers against the Omicron variant showed a significant reduction compared with those against wild type in both groups, they maintained 28.1 at 28-days after the AWcorna booster, four times stronger than those in the inactivated vaccine group, which registered only 6.4.

The clinical results demonstrate that heterologous boosting with an mRNA vaccine could induce higher antibodies against the COVID-19 virus than a homologous booster, according to the researchers.

Also, no serious adverse events were reported in the AWcorna booster group.

The researchers said this vaccine booster's effectiveness in preventing COVID-19 infection remains to be determined, but its potent antibody induction supports the emergency use as a heterologous booster in China.

The ongoing international phase-3 trials with 28,000 participants will provide more about the safety profile of AWcorna, said the researchers.