An Omicron-specific COVID-19 vaccine candidate developed by domestic producer Sinopharm has been approved for clinical trials by China's top drug regulator, the company said on Tuesday.

The experimental inactivated vaccine, if successful, is likely to be used as a third or fourth booster shot for fully vaccinated people aged 18 years and above.

China National Biotech Group, a subsidiary of Sinopharm, said in a statement released on its website the vaccine in the pipeline was already cleared for clinical trials in Hong Kong on April 13.

CNBG is the developer behind two inactivated vaccines widely used in China and worldwide. It began research into a vaccine targeting the Omicron variant in early December.

Pre-clinical studies and animal trials have shown the new vaccine can induce high levels of neutralizing antibodies against Omicron and several other variants.

Clinical trials will be rolled out among people above 18 who have already been vaccinated with two or three doses of COVID-19 vaccines.