China approved a recombinant protein subunit vaccine against COVID-19 for emergency use on March 17, its developer, the Chinese Academy of Sciences' Institute of Microbiology, said.

It is the first vaccine with the technique approved by the country for emergency use against COVID-19.

Currently, China has given conditional market approvals for four vaccines manufactured by Sinopharm, Sinovac and CanSino. Two by Sinopharm and one by Sinovac are inactivated vaccines, while CanSino makes adenoviral vector ones.

The new vaccine was developed by the institute and Anhui Zhifei Longcom Biopharmaceutical. It is currently in late-stage clinical trials in countries including Uzbekistan, Pakistan, Ecuador and Indonesia, with plans to inoculate 29,000 volunteers, the institute said on Monday.

On March 1, Uzbekistan's Ministry of Innovative Development said it had approved the vaccine for market use in the Central Asian nation under the name ZF-UZ-VAC2001.

Rather than injecting a whole inactivated pathogen to trigger an immune response, like previously approved vaccines, subunit protein vaccines contain purified pieces of the virus's protein to train the immune system. These fragments are incapable of causing disease, making such vaccines very safe.

Notable subunit vaccines include the vaccine for hepatitis B. They do not need to be manufactured in high-biosecurity laboratories, have high output and low storage requirements, the institute said.

The vaccine completed early-and mid-stage clinical trials in October, and there were no severe adverse effects recorded, it said, adding the protection rate for the vaccine is on par with other COVID-19 recombinant subunit and mRNA vaccines. It did not disclose efficacy details.

US biotech company Novavax is the maker of another recombinant nanoparticle subunit vaccine for COVID called NVX-CoV2373, whose late-stage trials results, released last week, showed it was 96.4 percent effective against mild, moderate and severe disease caused by the original COVID-19 strain.

The mRNA vaccines developed by Pfizer and Moderna both have a protection rate of around 95 percent.